Showing papers in "Journal of Leukocyte Biology in 2004"
TL;DR: The current understanding of IFN‐γ ligand, receptor, ignal transduction, and cellular effects with a focus on macrophage responses and to a lesser extent, responses from other cell types that influence macrophages function during infection are reviewed.
Abstract: Interferon-gamma (IFN-gamma) coordinates a diverse array of cellular programs through transcriptional regulation of immunologically relevant genes. This article reviews the current understanding of IFN-gamma ligand, receptor, signal transduction, and cellular effects with a focus on macrophage responses and to a lesser extent, responses from other cell types that influence macrophage function during infection. The current model for IFN-gamma signal transduction is discussed, as well as signal regulation and factors conferring signal specificity. Cellular effects of IFN-gamma are described, including up-regulation of pathogen recognition, antigen processing and presentation, the antiviral state, inhibition of cellular proliferation and effects on apoptosis, activation of microbicidal effector functions, immunomodulation, and leukocyte trafficking. In addition, integration of signaling and response with other cytokines and pathogen-associated molecular patterns, such as tumor necrosis factor-alpha, interleukin-4, type I IFNs, and lipopolysaccharide are discussed.
3,589 citations
TL;DR: Multiple actions provide evidence for active participation of cathelicidin peptides in the regulation of the antimicrobial host defenses.
Abstract: Cathelicidins comprise a family of mammalian proteins containing a C-terminal cat- ionic antimicrobial domain that becomes active af- ter being freed from the N-terminal cathelin por- tion of the holoprotein. Many other members of this family have been identified since the first cathelicidin sequences were reported 10 years ago. The mature peptides generally show a wide spec- trum of antimicrobial activity and, more recently, some of them have also been found to exert other biological activities. The human cathelicidin pep- tide LL-37 is chemotactic for neutrophils, mono- cytes, mast cells, and T cells; induces degranula- tion of mast cells; alters transcriptional responses in macrophages; and stimulates wound vasculariza- tion and re-epithelialization of healing skin. The porcine PR-39 has also been involved in a variety of processes, including promotion of wound repair, induction of angiogenesis, neutrophils, chemo- taxis, and inhibition of the phagocyte NADPH ox- idase activity, whereas the bovine BMAP-28 in- duces apoptosis in transformed cell lines and acti- vated lymphocytes and may thus help with clearance of unwanted cells at inflammation sites. These multiple actions provide evidence for active participation of cathelicidin peptides in the regula- tion of the antimicrobial host defenses. J. Leukoc. Biol. 75: 000-000; 2004.
983 citations
TL;DR: Evidence supporting stable differentiation as the basis for macrophage functionl heterogeneity is equivocal and the concept of whether macrophages develop into functional subsets as opposed to continuously adapting their functional pattern in response to the changing environment of a progressive inflammatory response is important to resolve from the perspectives of therapeutic targeting and understanding the role of Macrophages in disease pathogenesis.
Abstract: There has been substantial research activity in the past decade directed at phenotyping macrophage lineages and defining macrophage functional subsets or patterns of activity. The emphasis over the past 2–3 years has been to divide macrophage functional patterns into type 1 (Th1-driven) or type 2 (Th2-driven) functions. However, a huge array of environmental factors (including cytokines, chemokines, pattern recognition receptors, hormones) differentially regulates macrophage response patterns, resulting in the display of numerous distinct, functional phenotypes. Upon stimulation, a macrophage does not display just a single set of functions but rather displays a progression of functional changes in response to the progressive changes in its microenvironment. The remarkable ability of monocytes and tissue macrophages to adapt to changes in their microenvironment challenges the thesis that macrophages displaying unique tissue-specific or response-specific, functional patterns represent distinct lineages. With the exception of mature osteoclasts and mature dendritic cells, evidence supporting stable differentiation as the basis for macrophage functional heterogeneity is equivocal. The concept of whether macrophages develop into functional subsets as opposed to continuously adapting their functional pattern in response to the changing environment of a progressive inflammatory response is important to resolve from the perspectives of therapeutic targeting and understanding the role of macrophages in disease pathogenesis.
715 citations
TL;DR: It is essential that efforts should be directed to conclusively determine whether the reported putative endogenous ligands of TLRs are a result of the endogenous molecules or of contaminant(s), before exploring further the implication and therapeutic potential of these putative TLR ligands.
Abstract: Extensive work has suggested that a number of endogenous molecules such as heat shock proteins (hsp) may be potent activators of the innate immune system capable of inducing proinflammatory cytokine production by the monocyte-macrophage system and the activation and maturation of dendritic cells. The cytokine-like effects of these endogenous molecules are mediated via the Toll-like receptor (TLR) signal-transduction pathways in a manner similar to lipopolysaccharide (LPS; via TLR4) and bacterial lipoproteins (via TLR2). However, recent evidence suggests that the reported cytokine effects of hsp may be a result of the contaminating LPS and LPS-associated molecules. The reasons for previous failure to recognize the contaminant(s) being responsible for the putative TLR ligands of hsp include failure to use highly purified hsp free of LPS contamination; failure to recognize the heat sensitivity of LPS; and failure to consider contaminant(s) other than LPS. Whether other reported putative endogenous ligands of TLR2 and TLR4 are a result of contamination of pathogen-associated molecular patterns is not clear. It is essential that efforts should be directed to conclusively determine whether the reported putative endogenous ligands of TLRs are a result of the endogenous molecules or of contaminant(s), before exploring further the implication and therapeutic potential of these putative TLR ligands.
715 citations
TL;DR: The functions of systemic macrophages are discussed and a large number of membranous and biochemical markers, which can assist in the identification of these cells are cataloged.
Abstract: The phenotypic differentiation of systemic macrophages that have infiltrated the central nervous system, pericytes, perivascular macrophages, and the "real" resident microglial cells is a major immunocytochemical and immunohistochemical concern for all users of cultures of brain cells and brain sections. It is not only important in assessing the purity of cell cultures; it is also of fundamental importance in the assessment of the pathogenetic significance of perivascular inflammatory phenomena within the brain. The lack of a single membranous and/or biochemical marker allowing conclusive identification of these cells is still a major problem in neurobiology. This review briefly discusses the functions of these cells and catalogs a large number of membranous and biochemical markers, which can assist in the identification of these cells.
531 citations
TL;DR: Key structural and functional features of the neutrophil NADPH oxidase and its protein components are described, including a consideration of transcriptional and post‐translational regulatory features.
Abstract: Neutrophils play an essential role in the body's innate defense against pathogens and are one of the primary mediators of the inflammatory response. To defend the host, neutrophils use a wide range of microbicidal products, such as oxidants, microbicidal peptides, and lytic enzymes. The generation of microbicidal oxidants by neutrophils results from the activation of a multiprotein enzyme complex known as the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which is responsible for transferring electrons from NADPH to O2, resulting in the formation of superoxide anion. During oxidase activation, cytosolic oxidase proteins translocate to the phagosome or plasma membrane, where they assemble around a central membrane-bound component known as flavocytochrome b. This process is highly regulated, involving phosphorylation, translocation, and multiple conformational changes. Originally, it was thought that the NADPH oxidase was restricted to phagocytes and used solely in host defense. However, recent studies indicate that similar NADPH oxidase systems are present in a wide variety of nonphagocytic cells. Although the nature of these nonphagocyte NADPH oxidases is still being defined, it is clear that they are functionally distinct from the phagocyte oxidases. It should be noted, however, that structural features of many nonphagocyte oxidase proteins do seem to be similar to those of their phagocyte counterparts. In this review, key structural and functional features of the neutrophil NADPH oxidase and its protein components are described, including a consideration of transcriptional and post-translational regulatory features. Furthermore, relevant details about structural and functional features of various nonphagocyte oxidase proteins will be included for comparison.
479 citations
TL;DR: Ex vivo endogenous mtDNA displays inflammatogenic properties as a result of its content of unmethylated CpG motifs and oxidatively damaged adducts, and extracellular mtDNA was detected in the synovial fluids of rheumatoid arthritis patients but not of control subjects.
Abstract: We report that mitochondrial DNA (mtDNA) is inflammatogenic in vitro and in vivo as a result of the presence of unmethylated CpG sequences and its oxidative status. Purified human and murine mtDNAs induced arthritis when injected intra-articularly (i.a.) in mice. Importantly, oligodeoxynucleotide that contained a single oxidatively damaged base also induced arthritis when injected i.a. in mice. In contrast, neither human nor murine nuclear DNA induced inflammation. mtDNA-induced arthritis was neither B cell- nor T cell-dependent but was mediated by monocytes/macrophages. mtDNA-induced nuclear factor-kappaB stimulation resulted in the production of tumor necrosis factor alpha, a potent, arthritogenic factor. Finally, extracellular mtDNA was detected in the synovial fluids of rheumatoid arthritis patients but not of control subjects. We conclude that endogenous mtDNA displays inflammatogenic properties as a result of its content of unmethylated CpG motifs and oxidatively damaged adducts.
407 citations
TL;DR: The innate immune system serves an important role in preventing microbial invasion, however, it experiences significant changes with advancing age, and natural killer cells from the elderly are less capable of destroying tumor cells.
Abstract: The innate immune system serves an important role in preventing microbial invasion. However, it experiences significant changes with advancing age. Among the age-associated changes are: Aged macrophages and neutrophils have impaired respiratory burst and reactive nitrogen intermediates as a result of altered intracellular signaling, rendering them less able to destroy bacteria. Aged neutrophils are also less able to respond to rescue from apoptosis. Aged dendritic cells (DC) are less able to stimulate T and B cells. The altered T cell stimulation is a result of changes in human leukocyte antigen expression and cytokine production, and lower B cell stimulation is a result of changes in DC immune complex binding. Natural killer (NK) cells from the elderly are less capable of destroying tumor cells. NK T cells increase in number and have greater interleukin-4 production with age. Levels of various complement components are also altered with advancing age.
339 citations
TL;DR: Recent fluorescence microscopic studies of phagocytosis in macrophages indicate that signaling by FcR occurs as a sequence of distinct stages, evident in the spatial and temporal patterns of phosphoinositides, protein kinase C, and Rho‐family GTPase activation on forming phagosomes.
Abstract: Phagocytosis by macrophages can be initiated by Fcgamma receptors (FcR) in membranes that bind to Fc regions of immunoglobulin G (IgG). Activated FcR transduce signals to cytoplasm, which regulate the internalization of IgG-coated particles into plasma membrane-derived vacuoles, phagosomes. Particles internalized by phagocytosis are much larger than FcR, which prompts questions of if and how the receptors are coordinated with each other. FcR-mediated signal transduction entails recruitment of proteins from cytoplasm to the receptor, largely via protein phosphorylation. These FcR signaling complexes then activate proteins that regulate actin, myosin, membrane fusion, and the production of reactive oxygen intermediates. Recent fluorescence microscopic studies of phagocytosis in macrophages indicate that signaling by FcR occurs as a sequence of distinct stages, evident in the spatial and temporal patterns of phosphoinositides, protein kinase C, and Rho-family GTPase activation on forming phagosomes. The coordination of these stages may be regulated by lipids or lipid-anchored proteins, which diffuse away from FcR complexes. Lateral diffusion of FcR-derived signals could integrate FcR-dependent responses over large areas of membrane in the forming phagosome.
317 citations
TL;DR: The data suggest that mice have a large reservoir of functionally competent neutrophils in their bone marrow, which may be needed to replace circulating neutrophil rapidly during infection.
Abstract: The mouse has become an important model for immunological studies including innate immunity. Creating transgenic mice offers unique possibilities to study gene-function relationships. However, relatively little is known about the physiology of neutrophils from wild-type mice. Do they behave like human neutrophils, or are there species-specific differences that need to be considered when extrapolating results from mice to humans? How do we isolate neutrophils from mice? For practical reasons, many studies on mouse neutrophils are done with bone marrow cells. However, human bone marrow neutrophils appear to be heterogeneous and frictionally immature. We have isolated and compared neutrophils from mouse bone marrow and from peripheral blood obtained by tail bleeding. Using the same Percoll® density gradient for both preparations, we have obtained morphologically mature neutrophils from bone marrow and blood. Both cell populations responded to formylmethionyl-leucyl-phenylalanine (fMLF) with primary and secondary granule release and superoxide production. Quantitative analysis of our data revealed minor differences between cells from bone marrow and blood. Superoxide production and primary granule release were stimulated at lower fMLF concentrations in blood neutrophils. However, the amplitude and the kinetics of maximal responses were similar. The principal difference was the lifespan of the two cell populations. Bone marrow cells survived significantly longer in culture, which may suggest that they are receiving antiapoptic signals that are absent in the blood. Our data suggest that mice have a large reservoir of functionally competent neutrophils in their bone marrow. This reservoir may be needed to replace circulating neutrophils rapidly during infection.
292 citations
TL;DR: The receptors for these cytokines are often present on cell lines derived from various tumors, including liver, colorectal, and pancreatic carcinomas, and may provide novel targets for inhibiting the growth of certain types of cancer.
Abstract: Several novel interleukin (IL)-10-related cytokines have recently been discovered These include IL-22, IL-26, and the interferon-lambda (IFN-lambda) proteins IFN-lambda1 (IL-29), IFN-lambda2 (IL-28A), and IFN-lambda3 (IL-28B) The ligand-binding chains for IL-22, IL-26, and IFN-lambda are distinct from that used by IL-10; however, all of these cytokines use a common second chain, IL-10 receptor-2 (IL-10R2; CRF2-4), to assemble their active receptor complexes Thus, IL-10R2 is a shared component in at least four distinct class II cytokine-receptor complexes IL-10 binds to IL-10R1; IL-22 binds to IL-22R1; IL-26 binds to IL-20R1; and IFN-lambda binds to IFN-lambdaR1 (also known as IL-28R) The binding of these ligands to their respective R1 chains induces a conformational change that enables IL-10R2 to interact with the newly formed ligand-receptor complexes This in turn activates a signal-transduction cascade that results in rapid activation of several transcription factors, particularly signal transducer and activator of transcription (STAT)3 and to a lesser degree, STAT1 Activation by IL-10, IL-22, IL-26, or IFN-lambda can be blocked with neutralizing antibodies to the IL-10R2 chain Although IL-10R2 is broadly expressed on a wide variety of tissues, only a subset of these tissues expresses the ligand-binding R1 chains The receptors for these cytokines are often present on cell lines derived from various tumors, including liver, colorectal, and pancreatic carcinomas Consequently, the receptors for these cytokines may provide novel targets for inhibiting the growth of certain types of cancer
TL;DR: The crucial role of TLRs for the host defense against infections has been strengthened recently by the description of patients partially defective in the TLR‐activation pathways.
Abstract: Toll-like receptors (TLRs) have been identified as a major class of pattern-recognition receptors. Recognition of pathogen-associated molecular patterns (PAMPs) by TLRs, alone or in heterodimerization with other TLR or non-TLR receptors, induces signals responsible for the activation of genes important for an effective host defense, especially proinflammatory cytokines. Although a certain degree of redundancy exists between signals induced by the various TLRs, recent studies have identified intracellular pathways specific for individual TLRs. This leads to the release of cytokine profiles specific for particular PAMPs, and thus, TLRs confer a certain degree of specificity to the innate-immune response. In addition to the activation of the innate-immune response, TLR-mediated recognition represents a link between the innate- and acquired-immune systems, by inducing the maturation of dendritic cells and directing the T helper responses. Alternatively, recent data have also suggested TLR-mediated escape mechanisms used by certain pathogenic microorganisms, especially through TLR2 induction of anti-inflammatory cytokines. Finally, the crucial role of TLRs for the host defense against infections has been strengthened recently by the description of patients partially defective in the TLR-activation pathways.
TL;DR: Transgenic mice expressing an inducible suicide gene, which allows systemic and reversible elimination of macrophages, were developed and displayed several abnormalities, including splenomegaly, lymphadenopathy, thymic atrophy, extramedullary hematopoiesis, and development of peritoneal adhesions.
Abstract: Transgenic mice expressing an inducible suicide gene, which allows systemic and reversible elimination of macrophages, were developed. A macrophage-specific c-fms promoter was used to express enhanced green fluorescent protein and a drug-inducible suicide gene that leads to Fas-mediated apoptosis in resting and cycling cells of the macrophage lineage. Transgenic mice were fertile, of normal weight, and showed no abnormal phenotype before drug exposure. The transgene was expressed constitutively in macrophages and dendritic cells (DC) but not significantly in T cells or B cells. Induction of the suicide gene led to depletion of 70-95% of macrophages and DC in nearly all tissues examined. Depletion reduced the ability to clear bacteria from the blood and led to increased bacterial growth in the liver. Depleted mice displayed several abnormalities, including splenomegaly, lymphadenopathy, thymic atrophy, extramedullary hematopoiesis, and development of peritoneal adhesions. This new, transgenic line will be useful in investigating the role of macrophages and DC.
TL;DR: It is concluded that macrophages from aged mice exhibited suppressed proinflammatory cytokine production, which correlated with diminished total levels and LPS‐stimulated activation of p38 and JNK, which suggest that decreased MAPK expression could be a mechanism responsible for age‐related deterioration of the immune system.
Abstract: Age-related changes in immunity ren- der elderly individuals more susceptible to infec- tions than the young. Previous work by our lab- oratory and others showed that macrophages from aged mice are functionally impaired. Mac- rophages produce proinflammatory cytokines, tumor necrosis factor (TNF-) and interleukin (IL)-6, when stimulated with lipopolysaccharide (LPS), which signals through Toll-like receptor-4 (TLR4) and requires activation of mitogen-acti- vated protein kinases (MAPKs). We investigated whether aging is associated with alterations in TNF- and IL-6 production and MAPK expres- sion and activation in thioglycollate-elicited peri- toneal macrophages from mice. Kinetics and LPS dose-responsiveness of macrophage TNF- production did not differ by age. Although un- stimulated macrophages did not differ by age in their cytokine production, LPS-stimulated (100 ng/mL) cultures from aged mice produced 100 30 pg/mL TNF- and 6000 2000 pg/mL IL-6, and those from young mice produced 280 50 pg/mL and 10,650 10 pg/mL, respectively (P 25% reduction of total p38 and JNK in mac- rophages from aged mice relative to young. In addition, surface TLR4 levels did not vary with age. We conclude that macrophages from aged mice exhibited suppressed proinflammatory cy- tokine production, which correlated with dimin- ished total levels and LPS-stimulated activation of p38 and JNK. These observations suggest that decreased MAPK expression could be a mecha- nism responsible for age-related deterioration of the immune system. J. Leukoc. Biol. 75: 000 -0 00; 2004.
TL;DR: The activation of dendritic cells via Toll‐like receptors plays a decisive role in shaping the outcome of primary immune responses and the capacity of DC to integrate these factors and elicit distinct classes of immune responses is reviewed.
Abstract: The activation of dendritic cells (DC) via Toll-like receptors (TLRs) plays a decisive role in shaping the outcome of primary immune responses. Following TLR engagement by microbial products, DC migrate from peripheral tissues to lymphoid organs and up-regulate major histocompatibility complex and costimulatory molecules, acquiring the unique capacity to prime pathogen-specific, naive T cells. In addition, DC determine the character of the ensuing immune response by secreting cytokines that drive the development of T cells into T helper cell type 1 (Th1), Th2, or T regulatory effector cells. Three major factors influence the pattern of cytokines released by DC and accordingly, the Th balance: the lineage to which DC belong; the maturation stimulus; and inflammatory mediators present at the site of infection. A major focus of this review is the capacity of DC to integrate these factors and elicit distinct classes of immune responses.
TL;DR: SR‐PSOX/CXCL16 is a unique molecule that not only attracts T cells and NKT cells toward DCs but also supports their firm adhesion to DCs.
Abstract: Direct contacts between dendritic cells (DCs) and T cells or natural killer T (NKT) cells play important roles in primary and secondary immune responses. SR-PSOX/CXC chemokine ligand 16 (CXCL16), which is selectively expressed on DCs and macrophages, is a scavenger receptor for oxidized low-density lipoprotein and also the chemokine ligand for a G protein-coupled receptor CXC chemokine receptor 6 (CXCR6), expressed on activated T cells and NKT cells. SR-PSOX/CXCL16 is the second transmembrane-type chemokine with a chemokine domain fused to a mucin-like stalk, a structure very similar to that of fractalkine (FNK). Here, we demonstrate that SR-PSOX/CXCL16 functions as a cell adhesion molecule for cells expressing CXCR6 in the same manner that FNK functions as a cell adhesion molecule for cells expressing CX(3)C chemokine receptor 1 (CX(3)CR1) without requiring CX(3)CR1-mediated signal transduction or integrin activation. The chemokine domain of SR-PSOX/CXCL16 mediated the adhesion of CXCR6-expressing cells, which was not impaired by treatment with pertussis toxin, a Galphai protein blocker, which inhibited chemotaxis of CXCR6-expressing cells induced by SR-PSOX/CXCL16. Furthermore, the adhesion activity was up-regulated by treatment of SR-PSOX/CXCL16-expressing cells with a metalloprotease inhibitor, which increased surface expression levels of SR-PSOX/CXCL16. Thus, SR-PSOX/CXCL16 is a unique molecule that not only attracts T cells and NKT cells toward DCs but also supports their firm adhesion to DCs.
TL;DR: This study demonstrates that IL‐17 and tumor necrosis factor α (TNF‐α) cooperatively induce the lipopolysaccharide‐inducible CXC chemokine (LIX), the first demonstration of LIX expression in bone cells and has implications for inflammatory bone diseases such as arthritis and periodontal disease.
Abstract: Interleukin (IL)-17 is the founding member of an emerging family of inflammatory cytokines whose functions remain poorly defined. IL-17 has been linked to the pathogenesis of rheumatoid arthritis, and numerous studies implicate this cytokine in inflammation-induced bone loss. It is clear that a major function of IL-17 is to amplify the immune response by triggering production of chemokines, cytokines, and cell-surface markers, ultimately leading to neutrophil chemotaxis and inflammation. As an IL-17 signaling deficiency in mice causes a dramatic reduction in neutrophil chemotaxis and a consequent increased susceptibility to bacterial infection, it is important to define gene targets involved in IL-17-mediated neutrophil trafficking. Here, we demonstrate that IL-17 and tumor necrosis factor alpha (TNF-alpha) cooperatively induce the lipopolysaccharide-inducible CXC chemokine (LIX; a.k.a., CXC chemokine ligand 5, Scya5, or murine granulocyte chemotactic protein-2) in the preosteoblast cell line MC3T3. LIX is induced rapidly at the mRNA and protein levels, likely through the activation of new gene transcription. Conditioned media from MC3T3 cells treated with IL-17 and/or TNF-alpha stimulates neutrophil mobility potently, and LIX is a significant contributing factor to this process. In addition, IL-17 cooperates with bacterial components involved in periodontal disease to up-regulate LIX expression. This study is the first demonstration of LIX expression in bone cells and has implications for inflammatory bone diseases such as arthritis and periodontal disease.
TL;DR: The results show that human monocyte‐derived DCs respond differently to different Gram‐positive bacteria, and stimulation with nonpathogenic L. rhamnosus resulted in development of semi‐mature DCs characterized by moderate expression of costimulatory molecules and low cytokine production.
Abstract: Dendritic cells (DCs) are the most efficient antigen-presenting cells and thus, have a major role in regulating host immune responses. In the present study, we have analyzed the ability of Gram-positive, pathogenic Streptococcus pyogenes and nonpathogenic Lactobacillus rhamnosus to induce the maturation of human monocyte-derived DCs. Stimulation of DCs with S. pyogenes resulted in strong expression of DC costimulatory molecules CD80, CD83, and CD86 accompanied with a T helper cell type 1 (Th1) cytokine and chemokine response. S. pyogenes also induced interleukin (IL)-2 and IL-12 production at mRNA and protein levels. In addition, IL-23 and IL-27 subunits p40, p19, p28, and EBI3 were induced at mRNA level. In contrast, L. rhamnosus-stimulated DCs showed only moderate expression of costimulatory molecules and produced low levels of cytokines and chemokines. Furthermore, no production of IL-2 or IL-12 family cytokines was detected. Bacteria-induced DC maturation and especially cytokine and chemokine production were reduced when bacteria were heat-inactivated. Our results show that human monocyte-derived DCs respond differently to different Gram-positive bacteria. Although pathogenic S. pyogenes induced a strong Th1-type response, stimulation with nonpathogenic L. rhamnosus resulted in development of semi-mature DCs characterized by moderate expression of costimulatory molecules and low cytokine production.
TL;DR: It is demonstrated that genetic disruption of CD14 expression abrogated LPS‐induced TNF production but only partially attenuated LPS •HMGB1 release in cultures of primary murine peritoneal macrophages, suggesting that LPS stimulates macrophage to release HMGB1 partly through CD14‐ and TNF‐dependent mechanisms.
Abstract: Bacterial endotoxin [lipopolysaccharide (LPS)] stimulates macrophages to sequentially release early [tumor necrosis factor (TNF)] and late [high mobility group box 1 (HMGB1)] proinflammatory cytokines. The requirement of CD14 and mitogen-activated protein kinases [MAPK; e.g., p38 and extracellular signal-regulated kinase (ERK)1/2] for endotoxin-induced TNF production has been demonstrated previously, but little is known about their involvement in endotoxin-mediated HMGB1 release. Here, we demonstrated that genetic disruption of CD14 expression abrogated LPS-induced TNF production but only partially attenuated LPS-induced HMGB1 release in cultures of primary murine peritoneal macrophages. Pharmacological suppression of p38 or ERK1/2 MAPK with specific inhibitors (SB203580, SB202190, U0126, or PD98059) significantly attenuated LPS-induced TNF production but failed to inhibit LPS-induced HMGB1 release. Consistently, an endogenous, immunosuppressive molecule, spermine, failed to inhibit LPS-induced activation of p38 MAPK and yet, still significantly attenuated LPS-mediated HMGB1 release. Direct suppression of TNF activity with neutralizing antibodies or genetic disruption of TNF expression partially attenuated HMGB1 release from macrophages induced by LPS at lower concentrations (e.g., 10 ng/ml). Taken together, these data suggest that LPS stimulates macrophages to release HMGB1 partly through CD14- and TNF-dependent mechanisms.
TL;DR: It is hypothesized that virally induced chemokine production plays a pivotal role in the homing of leukocytes to PDC.
Abstract: The natural interferon (IFN)-produc- ing cell is now known to be identical to the plasma- cytoid dendritic cell (PDC). These are Lin - , CD123, CD11c - , and human leukocyte antigen- DR cells that secrete large amounts of IFN- (1-2 IU/cell) when stimulated by enveloped viruses such as herpes simplex virus. In the current study, we have evaluated chemokine expression by virally stimulated PDC. Up-regulation of mRNA for CCL4, CCL3, CCL5, CCL2, and CXC chemokine ligand (CXCL)10 in herpes simplex virus-stimu- lated PDC was detected by RNAse protection as- says. In contrast, PDC-depleted peripheral blood mononuclear cells did not up-regulate these mRNA species upon viral stimulation. Enzyme-linked im- munosorbent assay and/or intracellular flow cy- tometry confirmed production of these proteins, and studies indicated overlapping production of IFN- and the other cytokines/chemokines by PDC. Endocytosis plays a critical role in chemo- kine induction, as disruption of the pathway inhib- its the response. However, transcription of viral genes is not required for chemokine induction. Autocrine IFN- signaling in the PDC could ac- count for a portion of the CXCL10 and CCL2 production in virally stimulated PDC but was not responsible for the induction of the other chemo- kines. To evaluate the functional role of the che- mokines, chemotaxis assays were performed using supernatants from virally stimulated PDC. Acti- vated T cells and natural killer cells, but not nao¨ve T cells, were preferentially recruited by these PDC supernatants. Migration was subsequently inhibited by addition of neutralizing antibody to CCL4 and CXCL10. We hypothesize that virally induced che- mokine production plays a pivotal role in the hom- ing of leukocytes to PDC. J. Leukoc. Biol. 75: 504-514; 2004.
TL;DR: The results highlight the potential of CXCR2 antagonists as therapy for COPD and demonstrate that an enhanced PBMC/monocyte response to specific CXC chemokines in these patients may contribute to increased recruitment and activation of macrophages in the lungs.
Abstract: Leukocyte migration is critical to maintaining host defense, but uncontrolled cellular infiltration into tissues can lead to chronic inflammation. In the lung, such diseases include chronic obstructive pulmonary disease (COPD), a debilitating, respiratory condition characterized by progressive and largely irreversible airflow limitation for which cigarette smoking is the major risk factor. COPD is associated with an increased inflammatory cell influx including increased macrophage numbers in the airways and tissue. Alveolar macrophages develop from immigrating blood monocytes and have the capacity to cause the pathological changes associated with COPD. This study addressed the hypothesis that increased macrophage numbers in COPD are a result of increased recruitment of monocytes from the circulation. Chemotaxis assays of peripheral blood mononuclear cells (PBMC)/monocytes from nonsmokers, smokers, and COPD patients demonstrated increased chemotactic responses for cells from COPD patients when compared with controls toward growth-related oncogene (GRO)alpha and neutrophil-activating peptide (NAP)-2 but not toward monocyte chemoattractant protein, interleukin-8, or epithelial-derived NAP(ENA)-78. The enhanced chemotactic response toward GROalpha and NAP-2 was not mediated by differences in expression of their cellular receptors, CXCR1 or CXCR2. Receptor expression studies using flow cytometry indicated that in COPD, monocyte expression of CXCR2 is regulated differently from nonsmokers and smokers, which may account for the enhanced migration toward GROalpha and NAP-2. The results highlight the potential of CXCR2 antagonists as therapy for COPD and demonstrate that an enhanced PBMC/monocyte response to specific CXC chemokines in these patients may contribute to increased recruitment and activation of macrophages in the lungs.
TL;DR: Results indicate that c‐RESV at micromolar concentrations significantly attenuates several components of the macrophage response to proinflammatory stimuli.
Abstract: This study investigated for the first time the effects of the cis isomer of resveratrol (c-RESV) on the responses of inflammatory murine peritoneal macrophages, namely on the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) during the respiratory burst; on the biosynthesis of other mediators of inflammation such prostaglandins; and on the expression of inflammatory genes such as inducible nitric oxide synthase (NOS)-2 and inducible cyclooxygenase (COX)-2. Treatment with 1-100 microM c-RESV significantly inhibited intracellular and extracellular ROS production, and c-RESV at 10-100 microM significantly reduced RNS production. c-RESV at 1-100 microM was ineffective for scavenging superoxide radicals (O(2)(.-)), generated enzymatically by a hypoxanthine (HX)/xanthine oxidase (XO) system and/or for inhibiting XO activity. However, c-RESV at 10-100 microM decreased nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase activity in macrophage homogenates. c-RESV at 100 microM decreased NOS-2 and COX-2 mRNA levels in lipopolysaccharide (LPS) interferon gamma (IFN-gamma)-treated macrophages. At 10-100 microM, c-RESV also significantly inhibited NOS-2 and COX-2 protein synthesis and decreased prostaglandin E(2) (PGE(2)) production. These results indicate that c-RESV at micromolar concentrations significantly attenuates several components of the macrophage response to proinflammatory stimuli (notably, production of O(2)(.-)(-) and of the proinflammatory mediators NO(.-) and PGE(2)).
TL;DR: Through its immunosuppressive prowess, TGF‐β effectively orchestrates resolution of inflammation and control of autoaggressive immune reactions by managing T cell anergy, defining unique populations of Treg cells, regulating T cell death, and influencing the host response to infections.
Abstract: Innate and adaptive immunity function to eliminate foreign invaders and respond to injury while enabling coexistence with commensal microbes and tolerance against self and innocuous agents. Although most often effective in accomplishing these objectives, immunologic processes are not fail-safe and may underserve or be excessive in protecting the host. Checks and balances to maintain control of the immune system are in place and are becoming increasingly appreciated as targets for manipulating immunopathologic responses. One of the most recognized mediators of immune regulation is the cytokine transforming growth factor-beta (TGF-beta), a product of immune and nonimmune cells. Emerging data have unveiled a pivotal role for TGF-beta as a perpetrator of suppression by CD4(+)CD25(+) regulatory T (Treg) cells and in apoptotic sequelae. Through its immunosuppressive prowess, TGF-beta effectively orchestrates resolution of inflammation and control of autoaggressive immune reactions by managing T cell anergy, defining unique populations of Treg cells, regulating T cell death, and influencing the host response to infections.
TL;DR: The migration index of B‐CLL cells in response to both of the CCR7 ligands correlated with the presence of clinical lymphadenopathy, thus indicating that the high expression of functional chemokine receptors justifies the widespread character of B-CLL, representing a clinical target for the control of tumor cell dissemination.
Abstract: B cell neoplasms present heteroge- neous patterns of lymphoid organ involvement, which may be a result of the differential expres- sion of chemokine receptors. We found that che- mokine receptor (CCR)7, CXC chemokine recep- tor (CXCR)4, or CXCR5, the main chemokine receptors that mediate B cell entry into second- ary lymphoid tissues and their homing to T cell and B cell zones therein, were highly expressed in B malignancies with widespread involvement of lymph nodes. Conversely, those pathologies with little or no nodular dissemination showed no expression to very low levels of CCR7 and CXCR5 and low to moderate levels of CXCR4. These findings provide evidence for the role of CCR7, CXCR4, and CXCR5 in determining the pattern of lymphoid organ involvement of B tu- mors. Functional studies were performed on B malignancies expressing different levels of CCR7, CXCR5, and CXCR4. Multiple myeloma (MM) cells did not express CCR7 nor CXCR5 and did not migrate in response to their ligands; a moderate expression of CXCR4 on MM cells was accompanied by a migratory response to its li- gand, CXCL12. By contrast, cells from B cell chronic lymphocytic leukemia (B-CLL) ex- pressed the highest levels of these chemokine receptors and efficiently migrated in response to all ligands of CCR7, CXCR4, and CXCR5. In addition, the migration index of B-CLL cells in response to both of the CCR7 ligands correlated with the presence of clinical lymphadenopathy, thus indicating that the high expression of func- tional chemokine receptors justifies the wide- spread character of B-CLL, representing a clin- ical target for the control of tumor cell dissemination. J. Leukoc. Biol. 76: 000 -0 00; 2004.
TL;DR: Significant progress has been made in defining the means by which phagocytes kill and dispose of microbes, and congeners of several of the APP have been developed as potential therapeutic agents and have entered clinical trials with some evidence of benefit.
Abstract: Phagocytic leukocytes are a central cellular element of innate-immune defense in mammals. Over the past few decades, substantial progress has been made in defining the means by which phagocytes kill and dispose of microbes. In addition to the generation of toxic oxygen radicals and nitric oxide, leukocytes deploy a broad array of antimicrobial proteins and peptides (APP). The majority of APP includes cationic, granule-associated (poly)peptides with affinity for components of the negatively charged microbial cell wall. Over the past few years, the range of cells expressing APP and the potential roles of these agents have further expanded. Recent advances include the discovery of two novel families of mammalian APP (peptidoglycan recognition proteins and neutrophil gelatinase-associated lipocalin), that the oxygen-dependent and oxygen-independent systems are inextricably linked, that APP can be deployed in the context of novel subcellular organelles, and APP and the Toll-like receptor system interact. From a clinical perspective, congeners of several of the APP have been developed as potential therapeutic agents and have entered clinical trials with some evidence of benefit.
TL;DR: It is interesting that anti‐4‐1BB‐mediated but not anti‐GITR‐directed inhibition was more potent when Tr cells were preactivated, and this data indicate that 4‐1 BB signaling is critical in Tr cell immunity.
Abstract: 4-1BB (CD137) is a costimulatorymolecule involved in the activation and survival ofCD4, CD8, and natural killer cells. Although agreat deal has been learned as to how 4-1BB-mediated signaling governs the immunity of con-ventional T cells, the functional role of 4-1BB inthe context of CD4 CD25 regulatory T cell (Tr)activation is largely unknown. Using 4-1BB-intactand -deficient mice, we investigated the effect ofthe 4-1BB/4-1BB ligand pathway on the suppres-sive function of Tr cells. Our data indicate thatalthough 4-1BB is expressed on Tr cells, its con-tribution to their proliferation is minimal. We alsoshowed that signaling through the 4-1BB receptorinhibited the suppressive function of Tr cells invitro and in vivo. It is interesting that anti-4-1BB-mediatedbutnotanti-GITR-directedinhibitionwasmore potent when Tr cells were preactivated. Col-lectively, these data indicate that 4-1BB signalingis critical in Tr cell immunity. J. Leukoc. Biol. 75:785–791; 2004. Key Words: regulatory T lymphocytes GVHD tolerance sup-pression
TL;DR: The studies suggest that although the chemokines detected may play a role in regulating leukocyte trafficking to the lung during influenza infection, some may be functionally redundant.
Abstract: Influenza A virus replicates in the respiratory epithelium and induces an inflammatory infiltrate comprised of mononuclear cells and neutrophils. To understand the development of the cell-mediated immune response to influenza and how leukocyte trafficking to sites of inflammation is regulated, we examined the chemokine expression pattern in lung tissue from A/PR/8/34-infected C57BL/6 mice using an RNase protection assay. Monocyte chemoattractant protein 1, macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, MIP-3alpha, regulated on activation, normal T expressed and secreted (RANTES), MIP-2, and interferon-inducible protein 10 (IP-10) mRNA expression was up-regulated between days 5 and 15 after infection, consistent with a role for these chemokines in leukocyte recruitment to the lung. Low levels of expression were detected for the CC chemokine receptors (CCR)2 and CCR5, whereas CXC chemokine receptor (CXCR)3 was significantly up-regulated by day 10 after infection, coinciding with peak inflammatory cell infiltration in the airways. As RANTES, IP-10, and their receptors were up-regulated during influenza virus infection, we investigated leukocyte recruitment and viral clearance in mice deficient in RANTES or CXCR3, the receptor for IP-10. Leukocyte recruitment and viral replication in influenza-infected RANTES knockout(-/-) mice were similar to that in control mice, showing that RANTES is not essential for the immune response to influenza infection. Similarly, leukocyte recruitment and viral replication in CXCR3-/- mice were identical to control mice, except at day 8 postinfection, where fewer lymphocytes, neutrophils, and eosinophils were detected in the bronchoalveolar lavage of CXCR3-/- mice. These studies suggest that although the chemokines detected may play a role in regulating leukocyte trafficking to the lung during influenza infection, some may be functionally redundant.
TL;DR: Treatment with SOD significantly reduces peroxidation reactions in the inflamed colon and affords significant amelioration of colonic inflammatory changes in experimental colitis.
Abstract: Oxidant stress has been implicated in the pathogenesis of inflammatory bowel disease. Antioxidant enzymes, such as superoxide dis- mutase (SOD), are candidate drugs for modulat- ing this pathogenic factor. This study was de- signed to determine the therapeutic value of SOD in an experimental model of colitis and to study the mechanisms underlying its effects on intestinal inflammation. For that purpose, colitic (trinitrobenzene sulfonic acid-induced) and con- trol rats were studied. Groups of colitic animals were treated with different doses of SOD (1, 4, or 13 mg/kg/day) or vehicle, starting after induc- tion of colitis and during 7 days. Clinical and pathological markers of colitis severity and lipid peroxidation in colonic tissue were measured. Leukocyte-endothelial cell interactions in co- lonic venules and expression of vascular cell ad- hesion molecule 1 (VCAM-1) were determined. Development of colitis was associated with a sig- nificant loss in body weight, an increase in mac- roscopic and microscopic damage scores, and colonic myeloperoxidase activity. Administra- tion of SOD significantly attenuated these changes in a dose-dependent manner and re- duced lipid peroxidation in colonic tissue. The increase in leukocyte rolling and adhesion in co- lonic venules of colitic rats were significantly reduced by administration of SOD, 13 mg/kg/ day. Development of colitis was associated with a marked increase in endothelial VCAM-1 expres- sion, which was significantly reduced by treat- ment with SOD. In conclusion, treatment with SOD significantly reduces peroxidation reactions in the inflamed colon and affords significant ame- lioration of colonic inflammatory changes in ex- perimental colitis. This effect is related to a re- duction in VCAM-1 expression and leukocyte re- cruitment into the inflamed intestine. J. Leukoc. Biol. 76: 000 -0 00; 2004.
TL;DR: The ability of these peptides to act as chemoattractants for cells of the innate‐ and adaptive‐immune system may also play an important role in perpetuating chronic inflammation in the GI tract.
Abstract: The gastrointestinal (GI) tract is exposed to a wide range of microorganisms. The expression of antimicrobial peptides has been demonstrated in different regions of the GI tract, predominantly in epithelial cells, which represent the first host cells with which the microorganisms have to interact for invasion. The intestinal epithelial monolayer is complex, consisting of different cell types, and most have a limited lifespan. Of the GI antimicrobial peptides, alpha- and beta-defensins have been studied the most and are expressed by distinct types of epithelial cells. Enteric alpha-defensin expression is normally restricted to Paneth and intermediate cells in the small intestine. However, there are important differences between mice and humans in the processing of the precursor forms of enteric alpha-defensins. Parasite infection induces an increase in the number of enteric alpha-defensin-expressing Paneth and intermediate cells in the murine small intestine. In the chronically inflamed colonic mucosa, metaplastic Paneth cells (which are absent in the normal colon) also express enteric alpha-defensins. Epithelial expression of beta-defensins may be constitutive or inducible by infectious and inflammatory stimuli. The production of some members of the beta-defensin family appears to be restricted to distinct parts of the GI tract. Recent studies using genetically manipulated rodents have demonstrated the likely in vivo importance of enteric antimicrobial peptides in innate host defense against microorganisms. The ability of these peptides to act as chemoattractants for cells of the innate- and adaptive-immune system may also play an important role in perpetuating chronic inflammation in the GI tract.
TL;DR: Evidence is provided for a role of PTX3 as an important component of the innate‐immune response and as part of the host mechanisms that control fungal recognition and phagocytosis.
Abstract: Pentraxin 3 (PTX3) is a tumor necrosis factor and interleukin-1beta-stimulated gene that encodes a long PTX with proinflammatory activity. Here, we show that peritoneal macrophages derived from PTX3 transgenic (Tg) mice express higher levels of PTX3 mRNA than macrophages from wild-type (WT) mice, at basal level as well as upon stimulation with zymosan (Zy). Macrophages from Tg mice also showed improved opsonin-independent phagocytosis of Zy particles and the yeast form of the fungus Paracoccidioides brasiliensis. In the case of P. brasiliensis, an enhanced microbicidal activity accompanied by higher production of nitric oxide was also observed in macrophages from Tg mice. Using fluorescein-activated cell sorter analysis and reverse transcriptase-polymerase chain reaction, we demonstrated that basal level of Toll-like receptor-6 and Zy-induced dectin-1 expression was slightly but consistently higher in macrophages from Tg mice than in macrophages from WT mice. Recombinant (r)PTX3 protein binds to Zy particles as well as to yeast cells of P. brasiliensis and addition of rPTX3, to a culture of WT-derived macrophages containing Zy leads to an increase in the phagocytic index, which parallels that of Tg-derived macrophages, demonstrating the opsonin-like activity of PTX3. It is important that blockade of dectin-1 receptor inhibited the phagocytosis of Zy particles by WT and PTX3 Tg macrophages, pointing out the relevant role of dectin-1 as the main receptor involved in Zy uptake. Our results provide evidence for a role of PTX3 as an important component of the innate-immune response and as part of the host mechanisms that control fungal recognition and phagocytosis.