Traffic signals for lymphocyte recirculation and leukocyte emigration: The multistep paradigm

Nearly a century after the significance of the human complement system was recognized, we have come to realize that its functions extend far beyond the elimination of microbes. Complement acts as a rapid and efficient immune surveillance system that has distinct effects on healthy and altered host cells and foreign intruders. By eliminating cellular debris and infectious microbes, orchestrating immune responses and sending 'danger' signals, complement contributes substantially to homeostasis, but it can also take action against healthy cells if not properly controlled. This review describes our updated view of the function, structure and dynamics of the complement network, highlights its interconnection with immunity at large and with other endogenous pathways, and illustrates its multiple roles in homeostasis and disease.

/pdf/complement-a-key-system-for-immune-surveillance-and-56fp7muk7t.pdf

Complement: a key system for immune surveillance and homeostasis

▪ Abstract Recent studies showing that detergent-resistant membrane fragments can be isolated from cells suggest that biological membranes are not always in a liquid-crystalline phase. Instead, sph...

Functions of lipid rafts in biological membranes.

Src family protein tyrosine kinases are activated following engagement of many different classes of cellular receptors and participate in signaling pathways that control a diverse spectrum of receptor-induced biological activities. While several of these kinases have evolved to play distinct roles in specific receptor pathways, there is considerable redundancy in the functions of these kinases, both with respect to the receptor pathways that activate these kinases and the downstream effectors that mediate their biological activities. This chapter reviews the evidence implicating Src family kinases in specific receptor pathways and describes the mechanisms leading to their activation, the targets that interact with these kinases, and the biological events that they regulate.

Cellular functions regulated by src family kinases

Publisher Summary This chapter focuses on interleukin-8 (IL-8) and related chemotactic cytokines—namely, CXC and CC chemokines. IL-8 is the best known member of a new class of cytokines that are widely studied because of their ability to attract and activate leukocytes, and their potential role as mediators of inflammation. IL-8 was originally isolated from the culture supernatants of stimulated human blood monocytes and was identified as a protein of 72 amino acids with a molecular weight of 8383. The three-dimensional structure of IL-8 has been studied by nuclear magnetic resonance spectroscopy and X-ray crystallography. In concentrated solution, and on crystallization, IL-8 is present as a dimer. The first CC chemokine was identified after cloning by differential hybridization from human tonsillar lymphocytes and was termed LD78. The CC and CXC chemokines are similar in size and have an overall structure that is characterized by the two intrachain disulfide bonds, short N-terminal and long C-terminal sequences. It discusses the role of chemokines in pathology with skin inflammation because psoriasis was the first disease to be linked to overproduction of IL-8. Several independent studies document the occurrence of high levels of IL-8 in the synovial fluid of inflamed joints of patients with different forms of rheumatic diseases, osteoarthritis, and gout.

Interleukin-8 and related chemotactic cytokines--CXC and CC chemokines.

Movement of neutrophils from the bloodstream to inflamed tissue depends on the activation of both the neutrophil and the endothelial cell. Endothelial cells lining the postcapillary venule respond to proinflammatory mediators by expressing adhesion molecules and synthesizing a variety of neutrophil-activating factors. Endothelial cell production of a 77-amino acid variant of interleukin-8 (IL-8) was found to be a requirement for the invasion of neutrophils through a vessel wall model. IL-8 secreted by cytokine- or lipopolysaccharide-stimulated endothelial cells induced the rapid shedding of neutrophil lectin adhesion molecule-1, the up-regulation of leukocyte beta 2 integrins, and the attachment and transmigration of the neutrophils. Thus, endogenous endothelial IL-8 regulates transvenular traffic during acute inflammatory responses.

https://science.sciencemag.org/content/sci/254/5028/99.full.pdf

Regulation of transendothelial neutrophil migration by endogenous interleukin-8

Immunologic classification of leukemia and lymphoma.

Mononuclear phagocytes (Mphi) produce urokinase-type plasminogen activator (uPA) and also express a specific cell-surface receptor for urokinase, uPAR. The concomitant expression of these proteins provides a mechanism by which Mphi can degrade extracellular matrix proteins during directed cell migration. In this study, we sought to determine if uPAR plays a role in Mphi chemotaxis that is distinct from its role in matrix proteolysis. Exposing adherent monocytes to a chemotactic gradient causes plasma membrane uPAR to localize strongly to the leading edge of cell migration. Adherence alone or exposure to FMLP had no effect on uPAR expression. Using Boyden chamber chemotaxis assays, we demonstrate that treating mononuclear cells with an anti-uPAR mAb (either as an intact mAb or F[ab']2) ablates chemotaxis induced by FMLP and monocyte chemotactic peptide-1 (P < 0.001). Inactivating the catalytic activity of uPAR-bound uPA had no effect on chemotaxis. Similarly, blocking uPAR expression with an antisense oligonucleotide to uPAR completely ablates chemotaxis, but blocking uPA expression with an antisense oligonucleotide to uPA has a minimal effect. We therefore demonstrate that expression and unimpeded function of uPAR plays an obligate role in M phi chemotaxis by mechanisms that are largely independent of its ligand, uPA. Combined with its known role in mediating pericellular proteolysis, these observations demonstrate that uPAR is essential for both locomotion and traversing tissue barriers during M phi migration.

/pdf/the-urokinase-receptor-is-required-for-human-monocyte-1dfz3ebwa5.pdf

The urokinase receptor is required for human monocyte chemotaxis in vitro.

We have shown previously that the urokinase-type plasminogen activator receptor (uPAR) physically associates with β2 integrins on human leukocyte membranes We now report that uPAR associates with certain members of the β1 and β3 integrin families expressed by a nonhematopoietic fibrosarcoma cell line (HT1080) when adherent to certain extracellular matrix molecules Flow cytometry studies indicated that HT1080 cells expressed uPAR and β1 and β3 integrins Double staining immunofluorescence was used to label uPAR and β1 and β3 integrins The staining patterns of uPAR and β1 integrins were strikingly similar when attached to fibronectin, laminin, or vitronectin but not polylysine-coated substrates Resonance energy transfer (RET) between uPAR and β1 integrins was observed, especially at focal adhesion plaques; this indicates that these molecules are within about 7 nm of each other on these cell membranes uPAR and β3 integrin coclustering and RET were also observed on tumor cells adherent to vitronectin but not to fibronectin, laminin, or polylysine-coated surfaces Because N -acetyl-d-glucosamine was found previously to inhibit β2 integrin-uPAR association, we tested the effect of saccharides on the β1-uPAR and β3-uPAR colocalization and RET Colocalization and RET between uPAR and β1 or β3 integrins were effectively inhibited by N -acetyl-d-glucosamine on extracellular matrix-coated surfaces To better define which members of β1 and β3 integrin families associate with uPAR, we studied the association of several α subunits with uPAR on tumor cells We found that: ( a ) α5 colocalizes with uPAR on cells attached to fibronectin-coated surfaces; ( b ) α5 and αv colocalize with uPAR on cells adherent to vitronectin; and ( c ) α3 and α6 associate with uPAR on cells attached to laminin In further support of physical associations between integrins and uPAR on tumor cells, uPAR was found to coimmunoprecipitate with β1 integrins in Brij-58 lysates of HT1080 cells (as detected by anti-uPAR Western blotting of material isolated from an anti-β1 integrin immunoaffinity column) Thus, uPAR may laterally associate with integrins of tumor cells when attached to specific extracellular matrix elements to enable directional proteolysis for tumor cell migration and invasion

/pdf/urokinase-type-plasminogen-activator-receptors-associate-21iymhq94j.pdf

Urokinase-Type Plasminogen Activator Receptors Associate with β1 and β3 Integrins of Fibrosarcoma Cells: Dependence on Extracellular Matrix Components

We investigated the effect of an anti-CD11b monoclonal antibody (1B6c) on ischemic cell damage after transient middle cerebral artery occlusion. We divided animals into three groups: MAb 1 group (n = 5)--rats were subjected to 2 hours of transient occlusion and 1B6c (1 mg/kg) was administered intravenously at 0 and 22 hours of reperfusion; MAb 2 group (n = 5)--same experimental protocol as MAb 1 group, except that the initial dose of 1B6c was increased to 2 mg/kg; and control group (n = 5)--same experimental protocol as MAb 2 group, except that an isotype-matched control antibody was administered. Animals were weighed and tested for neurological function before and after occlusion of the middle cerebral artery. Forty-six hours after reperfusion, brain sections were stained with hematoxylin and eosin for histology evaluation. We observed a significant reduction of weight loss and improvement in neurological function after ischemia in the MAb 2 animals compared to MAb 1 and vehicle-treated animals (p < 0.05). The lesion volume was significantly smaller in the MAb 2 group (19.5 +/- 1.9%) compared to MAb 1 (29.9 +/- 2.6%) and vehicle-treated (34.2 +/- 5.4%) groups (p < 0.01). Tissue polymorphonuclear cell numbers were reduced in both 1B6c-administered groups. Our data demonstrate that administration of anti-CD11b antibody results in a dose-dependent, significant functional improvement and reduction of ischemic cell damage after transient focal cerebral ischemia in the rat.

Robert F. Todd

Papers

Regulation of transendothelial neutrophil migration by endogenous interleukin-8

Immunologic classification of leukemia and lymphoma.

The urokinase receptor is required for human monocyte chemotaxis in vitro.

Urokinase-Type Plasminogen Activator Receptors Associate with β1 and β3 Integrins of Fibrosarcoma Cells: Dependence on Extracellular Matrix Components

Anti‐CD11b monoclonal antibody reduces ischemic cell damage after transient focal cerebral ischemia in rat