Showing papers on "Antigen published in 1991"

The dendritic cell system and its role in immunogenicity

Abstract: Dendritic cells are a system of antigen presenting cells that function to initiate several immune responses such as the sensitization of MHC-restricted T cells, the rejection of organ transplants, and the formation of T-dependent antibodies. Dendritic cells are found in many nonlymphoid tissues but can migrate via the afferent lymph or the blood stream to the T-dependent areas of lymphoid organs. In skin, the immunostimulatory function of dendritic cells is enhanced by cytokines, especially GM-CSF. After foreign proteins are administered in situ, dendritic cells are a principal reservoir of immunogen. In vitro studies indicate that dendritic cells only process proteins for a short period of time, when the rate of synthesis of MHC products and content of acidic endocytic vesicles are high. Antigen processing is selectively dampened after a day in culture, but the capacity to stimulate responses to surface bound peptides and mitogens remains strong. Dendritic cells are motile, and efficiently cluster and activate T cells that are specific for stimuli on the cell surface. High levels of MHC class-I and -II products and several adhesins, such as ICAM-1 and LFA-3, likely contribute to these functions. Therefore dendritic cells are specialized to mediate several physiologic components of immunogenicity such as the acquisition of antigens in tissues, the migration to lymphoid organs, and the identification and activation of antigen-specific T cells. The function of these presenting cells in immunologic tolerance is just beginning to be studied.

A gene encoding an antigen recognized by cytolytic T lymphocytes on a human melanoma

Abstract: Many human melanoma tumors express antigens that are recognized in vitro by cytolytic T lymphocytes (CTLs) derived from the tumor-bearing patient. A gene was identified that directed the expression of antigen MZ2-E on a human melanoma cell line. This gene shows no similarity to known sequences and belongs to a family of at least three genes. It is expressed by the original melanoma cells, other melanoma cell lines, and by some tumor cells of other histological types. No expression was observed in a panel of normal tissues. Antigen MZ2-E appears to be presented by HLA-A1; anti-MZ2-E CTLs of the original patient recognized two melanoma cell lines of other HLA-A1 patients that expressed the gene. Thus, precisely targeted immunotherapy directed against antigen MZ2-E could be provided to individuals identified by HLA typing and analysis of the RNA of a small tumor sample.

Transgenic non-human animals capable of producing heterologous antibodies

Abstract: The invention relates to transgenic non-human animals capable of producing heterologous antibodies and methods for producing human sequence antibodies which bind to human antigens with substantial affinity.

Interleukin 10 (IL-10) and viral IL-10 strongly reduce antigen-specific human T cell proliferation by diminishing the antigen-presenting capacity of monocytes via downregulation of class II major histocompatibility complex expression.

Abstract: Interleukin 10 (IL-10) and viral IL-10 (v-IL-10) strongly reduced antigen-specific proliferation of human T cells and CD4+ T cell clones when monocytes were used as antigen-presenting cells. In contrast, IL-10 and v-IL-10 did not affect the proliferative responses to antigens presented by autologous Epstein-Barr virus-lymphoblastoid cell line (EBV-LCL). Inhibition of antigen-specific T cell responses was associated with downregulation of constitutive, as well as interferon gamma- or IL-4-induced, class II MHC expression on monocytes by IL-10 and v-IL-10, resulting in the reduction in antigen-presenting capacity of these cells. In contrast, IL-10 and v-IL-10 had no effect on class II major histocompatibility complex (MHC) expression on EBV-LCL. The reduced antigen-presenting capacity of monocytes correlated with a decreased capacity to mobilize intracellular Ca2+ in the responder T cell clones. The diminished antigen-presenting capacities of monocytes were not due to inhibitory effects of IL-10 and v-IL-10 on antigen processing, since the proliferative T cell responses to antigenic peptides, which did not require processing, were equally well inhibited. Furthermore, the inhibitory effects of IL-10 and v-IL-10 on antigen-specific proliferative T cell responses could not be neutralized by exogenous IL-2 or IL-4. Although IL-10 and v-IL-10 suppressed IL-1 alpha, IL-1 beta, tumor necrosis factor alpha (TNF-alpha), and IL-6 production by monocytes, it was excluded that these cytokines played a role in antigen-specific T cell proliferation, since normal antigen-specific responses were observed in the presence of neutralizing anti-IL-1, -IL-6, and -TNF-alpha mAbs. Furthermore, addition of saturating concentrations of IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha to the cultures had no effect on the reduced proliferative T cell responses in the presence of IL-10, or v-IL-10. Collectively, our data indicate that IL-10 and v-IL-10 can completely prevent antigen-specific T cell proliferation by inhibition of the antigen-presenting capacity of monocytes through downregulation of class II MHC antigens on monocytes.

Lpr and gld: single gene models of systemic autoimmunity and lymphoproliferative disease.

Abstract: The autosomal recessive lpr and gld genes induce in mice multiple autoantibodies and the progressive accumulation of large numbers of non-malignant CD4- CD8- T lymphocytes. The clinical syndromes and immune abnormalities associated with these two nonallelic genes are nearly identical and are also highly dependent on background genes. MRL/lpr mice are particularly severely affected, and they develop a syndrome that is serologically and pathologically similar to human systemic lupus erythematosus (SLE). Abnormal cell marker expression in the aberrant lpr T lymphocytes includes surface antigens normally associated with activated T cells or even with B cells, and it occurs along with enhanced expression of certain oncogenes. The lpr gene results in intrinsic abnormalities of both T and B lymphocytes, yet its location and product are unknown. The gld gene is located on chromosome 1; its product is also unknown. Although many immunological abnormalities are known, the mechanism whereby these two genes induce au...

T-lymphocyte entry into the central nervous system

Abstract: The entry of T-lymphocytes into the parenchyma of the central nervous system is a critical early feature in the pathogenesis of many experimental and spontaneously occurring immune-mediated illnesses. The physiological mechanisms controlling this entry have not been elucidated. This study reports that T-cell entry into the rat CNS appears to be primarily dependent upon the activation state of the lymphocytes; T-lymphoblasts enter the CNS (and all other tissues examined) in an apparently random manner while T cells not in blast phase are excluded. Antigen specificity, MHC compatibility, T-cell phenotype, and T-cell receptor gene usage do not appear related to the ability of cells to enter. This study demonstrates that when T-lymphoblasts are introduced into the circulation they rapidly appear in the CNS tissue. Their concentration in the CNS reaches a peak between 9 and 12 hr, and lymphocytes which have entered, exit within 1 to 2 days. Cells capable of reacting with a CNS antigen remain in the tissue or cyclically reenter to initiate inflammation if they are able to recognize their antigen in the correct MHC context. This observation also appears to pertain to the entry of activated T cells into many other tissues, although their concentrations in these non-CNS sites was not quantitated.

Human immunodeficiency virus genetic variation that can escape cytotoxic T cell recognition.

Abstract: In a longitudinal study of HIV seropositive patients, there were fluctuations in the specificity of cytotoxic T cells for the virus. This was matched by variability in proviral gag DNA epitope sequences in the lymphocytes of these patients. Some of these viral variants are not recognized by autologous T cells. Accumulation of such mutations in T-cell antigenic targets would provide a mechanism for immune escape.

Interleukin-2 programs mouse alpha beta T lymphocytes for apoptosis.

Abstract: Antigen receptor stimulation of mature alpha beta T lymphocytes can lead either to proliferation or death. Programmed cell death, termed apoptosis, leads to the clonal deletion of both thymocytes and mature T cells that establishes tolerance. How a mature T cell selects between proliferation and death is not understood. Here I show that interleukin-2 (IL-2) is a critical determinant of the choice between these two fates. Both CD4+ and CD8+ T cells previously exposed to IL-2 undergo apoptosis after antigen-receptor stimulation. Antibody blockade of IL-2 but not IL-4 reverses the marked reduction of lymph node V beta 8+ T cells caused in mice by the bacterial superantigen Staphylococcus aureus enterotoxin B. IL-2 may thus participate in a feedback regulatory mechanism by predisposing mature T lymphocytes to apoptosis.

Development and function of T cells in mice rendered interleukin-2 deficient by gene targeting.

Abstract: Interleukin-2 (IL-2) is a lymphocytotropic hormone which is thought to have a key role in the immune response of mammalian cells. It is produced by a subpopulation of activated T-lymphocytes and acts in vitro as the principal auto- and paracrine T-cell growth factor (for reviews see refs 1-3). IL-2 is, however, not the sole T-cell growth factor, nor does it act exclusively on T cells, also promoting growth of NK cells and differentiation of B cells. A role for IL-2 in T-cell development has been postulated but remains controversial. Here we test the requirement for IL-2 in vivo using IL-2-deficient mice generated by targeted recombination. We find that mice homozygous for the IL-2 gene mutation are normal with regard to thymocyte and peripheral T-cell subset composition, but that a dysregulation of the immune system is manifested by reduced polyclonal in vitro T-cell responses and by dramatic changes in the isotype levels of serum immunoglobulins.

Immunobiochemical and molecular biologic characterization of the cell proliferation-associated nuclear antigen that is defined by monoclonal antibody Ki-67.

Abstract: The monoclonal antibody Ki-67 detects a human nuclear antigen that is present in proliferating cells, but absent in quiescent cells. The aim of this study was to characterize the Ki-67 antigen by means of immunobiochemical and molecular biology techniques. Enzymatic digestion experiments showed that this antigen is highly susceptible to protease treatment, and the antigen cannot be extracted by 0.1 normal HCl, indicating that Ki-67 antigen is a nonhistone protein. Immunoblot analysis of cell lysates with Ki-67 showed a double band with apparent molecular weights of 395 kd and 345 kd, regardless of whether the gels were run under reducing or nonreducing conditions. It is noteworthy that these bands were exclusively detectable in lysates prepared from proliferating cells, whereas they were absent in lysates obtained from quiescent cells. These immunobiochemical data are further substantiated by our molecular cloning approaches. By means of immunocloning with Ki-67, the authors isolated and sequenced several cDNA fragments from lambda gt11 libraries. A 1095-bp fragment gave a strong hybridization signal at 7.5 to 9.5 kb in Northern blot analysis with RNA prepared from proliferating cells, whereas it was negative with RNA prepared from quiescent cells. This cDNA fragment could be bacterially expressed, and in subsequent immunoblot analysis Ki-67 reacted exclusively with those fusion proteins that were derived from bacteria containing the insert in the right reading frame.

Enforced BCL2 expression in B-lymphoid cells prolongs antibody responses and elicits autoimmune disease

Abstract: The biological functions of the BCL2 gene were investigated in transgenic mice harboring human BCL2 cDNA under the control of an immunoglobulin heavy chain enhancer (E mu). Mice of a representative transgenic strain, E mu-bcl-2-22, had a great excess of B lymphocytes, immunoglobulin-secreting cells, and serum immunoglobulins, attributable to increased longevity of B-lineage cells. Pre-B and plasma cells as well as B cells exhibited prolonged survival in culture. Immunized animals produced an amplified and protracted antibody response. Within the first year of life, most mice spontaneously produced antibodies to nuclear antigens, and 60% developed kidney disease, diagnosed as immune complex glomerulonephritis. Thus E mu-bcl-2-22 mice constitute a transgenic model for a systemic autoimmune disease resembling the human disorder systemic lupus erythematosus.

ELAM-1 is an adhesion molecule for skin-homing T cells

Abstract: Endothelial cell leukocyte adhesion molecule-1 (ELAM-1) has been described as an inducible endothelial cell-adhesion molecule for neutrophils, and is believed to have a key role in the extravasation of these cells at sites of acute inflammation. Here we report that ELAM-1-transfected COS cells also bind a unique skin-associated subset of circulating memory T cells defined by the expression of the cutaneous lymphocyte-associated antigen. T cells expressing this antigen bind at least as well as neutrophils to expressed ELAM-1, whereas other lymphocytes in the peripheral blood bind poorly, or not at all. Immunohistological survey of chronically inflamed tissue specimens revealed that vascular expression of ELAM-1 occurs at cutaneous sites in preference to noncutaneous sites. We conclude that at sites of chronic inflammation, ELAM-1 may function as a skin vascular addressin, a tissue-selective endothelial cell-adhesion molecule for skin-homing memory T lymphocytes.

Downregulation of Th1 cytokine production accompanies induction of Th2 responses by a parasitic helminth, Schistosoma mansoni.

Abstract: In the mouse, infection with Schistosoma mansoni results in an egg-producing infection and associated disease, whereas vaccination with attenuated larval stages produces a substantial and specific immunity in the absence of egg-induced pathology. Preliminary data showing enhanced interleukin-5 (IL-5) production by T cells from infected mice and interferon gamma (IFN-gamma) synthesis by cells from vaccinated animals (7), suggested differential CD4+ subset stimulation by the different parasite stimuli. To confirm this hypothesis, lymphocytes from vaccinated or infected animals were compared for their ability to produce IFN-gamma and IL-2 (secreted by Th1 cells) as compared with IL-4 and IL-5 (characteristic Th2 cytokines). After stimulation with specific antigen or mitogen, T cells from vaccinated mice or prepatently infected animals responded primarily with Th1 lymphokines, whereas lymphocytes from patently infected mice instead produced Th2 cytokines. The Th2 response in infected animals was shown to be induced by schistosome eggs and directed largely against egg antigens, whereas the Th1 reactivity in vaccinated mice was triggered primarily by larval antigens. Interestingly, Th1 responses in mice carrying egg-producing infections were found to be profoundly downregulated. Moreover, the injection of eggs into vaccinated mice resulted in a reduction of antigen and mitogen-stimulated Th1 function accompanied by a coincident expression of Th2 responses. Together, the data suggest that coincident with the induction of Th2 responses, murine schistosome infection results in an inhibition of potentially protective Th1 function. This previously unrecognized downregulation of Th1 cytokine production may be an important immunological consequence of helminth infection related to host adaptation.

A large array of human monoclonal antibodies to type 1 human immunodeficiency virus from combinatorial libraries of asymptomatic seropositive individuals.

Abstract: A panel of human monoclonal antibody Fab fragments has been generated against the surface glycoprotein gp120 of type 1 human immunodeficiency virus (HIV) by antigen selection from a random combinatorial library expressed on the surface of filamentous phage. The library was prepared from 5 ml of bone marrow from an asymptomatic individual who has been HIV-positive for 6 years. The antibodies have high affinity for antigen (mostly with affinity constants of greater than 10(8) M-1) and notable sequence diversity. Given appropriate donor selection, the methods described should allow the generation of antibodies for the evaluation of passive immunization as a therapy for AIDS.

Treatment of established renal cancer by tumor cells engineered to secrete interleukin-4

Abstract: The generation of antigen-specific antitumor immunity is the ultimate goal in cancer immunotherapy. When cells from a spontaneously arising murine renal cell tumor were engineered to secrete large doses of interleukin-4 (IL-4) locally, they were rejected in a predominantly T cell-independent manner. However, animals that rejected the IL-4-transfected tumors developed T cell-dependent systemic immunity to the parental tumor. This systemic immunity was tumor-specific and primarily mediated by CD8+ T cells. Established parental tumors could be cured by the systemic immune response generated by injection of the genetically engineered tumors. These results provide a rationale for the use of lymphokine gene-transfected tumor cells as a modality for cancer therapy.

Sites of specific B cell activation in primary and secondary responses to T cell-dependent and T cell-independent antigens.

Abstract: Techniques which identify hapten-specific B cells in tissues have been used to determine the sites of B cell activation in rat spleens in response to T cell-dependent (TD) antigens and T cell-independent type-1 (TI-1) antigens. Surface-associated hapten binding by specific memory B cells and. B blasts was distinguished from the strong cytoplasmic hapten binding by specific plasma cells and plasmablasts. Blast cells in S phase were identified in tissue sections by staining cells which had been pulse labeled in vivo with 5-bromo-2′-deoxyuridine. Hapten-specific B blast cells are found in three sites: (a) around interdigitating cells in the T cell-rich zones; (b) in the follicular dendritic cell network and (c) in association with macrophages in the red pulp. Hapten-binding memory B cells, which are not in cell cycle, accumulate in the marginal zones and to a lesser extent the follicular mantles in response to TD and TI-1 antigens. The hapten-specific blast response in T zones is confined to the first few days after antigen is given and is low for primary responses to TD antigens, but massive on secondary challenge, when marginal zone memory B cells migrate to the T zones. Both the primary and secondary T zone responses to TI-1 antigens are impressive and in these responses hapten-specific B blasts are also found in the splenic red pulp. The follicular response to TD antigens starts with a small number of B blasts (fewer than five) entering each follicle. These increase in number exponentially so that by the 4th day after immunization they fill the follicle. The oligoclonality of the response is shown in simultaneous responses to two haptens where 6%–31% of the follicles on day 3 after immunization contain blasts specific for only one of the two haptens. During the 4th day classical zonal pattern of germinal centers develops. The surface immunoglobulin-positive B blasts are lost from the follicle center, while one pole of the follicular dendritic cell network fills with surface immunoglobulin-negative centroblasts. Centroblasts do not increase in numbers but divide to give rise to centrocytes, which re-express slg and migrate into the follicular dendritic cell network. Cell kinetic studies indicate that the centrocyte population is renewed from centroblasts every 7 h. Centrocytes either leave the germinal center within this time or die in situ. It is probable that the centroblasts and centrocytes are derived from the small number of B blasts which initiate the follicular reaction, for the centrocytes show the same oligoclonality observed at the B blast stage. The germinal center reaction declines gradually and 3 weeks after immunization centroblasts and centrocytes are no longer seen. At this time small clusters of B blasts can be found proliferating in the follicular dendritic cell network. These secondary B blasts characterize the third phase of the follicular reaction, which continues throughout the established phase of TD responses. Some follicular response is seen to TI-1 antigens but this is much less dramatic than that seen during TD responses.

Purified protein derivative of Mycobacterium tuberculosis and excretory-secretory antigen(s) of Toxocara canis expand in vitro human T cells with stable and opposite (type 1 T helper or type 2 T helper) profile of cytokine production.

Abstract: A large series of T cell clones (TCC) specific for purified protein derivative (PPD) of Mycobacterium tuberculosis (total 60) or Toxocara canis excretory/secretory (TES) antigen (total 69) were established from the peripheral blood of two healthy individuals and analyzed for their profile of cytokine production in response to stimulation with either the specific antigen or the polyclonal activator phorbol myristate acetate plus anti-CD3 antibody. Under both these experimental conditions, the great majority of PPD-specific TCC secreted IL-2 and IFN-gamma but not, or limited amounts of, IL-4 and IL-5. In contrast, most TES-specific TCC secreted IL-4 and IL-5 but not, or limited amounts of, IL-2 and IFN-gamma. PPD-specific TCC that failed to secrete IL-4 and IL-5, and TES-specific TCC that failed to secrete IL-2 and IFN-gamma, were found to lack transcripts for IL-4 and IL-5, or for IL-2 and IFN-gamma, respectively. During the course of the study, over a 6-mo period, the functional phenotype of both TES- and PPD-specific TCC was repeatedly assessed and remained constant. These data demonstrate that T cells with stable Th1 or Th2 functional pattern exist not only in mice but also in humans and suggest that in the course of natural immunization certain infectious agents preferentially expand T cell subsets with stable and definite profile of cytokine production.

A form of circulating ICAM-1 in human serum.

Abstract: A circulating form of the usually membrane-bound intercellular adhesion molecule-1 (ICAM-1) was identified and characterized in normal human serum, and in sera from patients with leukocyte adhesion deficiency (LAD). The molecule, designated circulating ICAM-1 (cICAM-1) was detected and quantitated by sandwich ELISA. Levels of cICAM-1 in sera from normal individuals ranged from 100 to 200 ng/ml. Sera from LAD patients had elevated cICAM-1 levels ranging from 200 to 700 ng/ml. The elevated levels of cICAM-1 in LAD sera may be due to an inability to adsorb cICAM-1 to cell-bound LFA-1 or may be an indirect result of the pathology accompanying the syndrome. cICAM-1 bound to mAb specific for four distinct ICAM-1 epitopes localized in domains D1, D2, D4, and D5, and displayed similar molecular size properties as recombinant soluble ICAM-1 on FPLC size-exclusion chromatography. When immobilized via a domain D5-specific mAb, cICAM-1 mediated function (LFA-1)-dependent lymphocyte adhesion equivalent to sICAM-1. These data indicate that cICAM-1 contains most, if not all, of the five extracellular domains of membrane ICAM-1, as well as the ability to bind specifically to LFA-1. The cellular source of cICAM-1 appeared to be from mononuclear cells; only lymphoid cell lines or primary PBMC cultures had detectable levels of cICAM-1 in cell culture supernatants. Because cICAM-1 retains the ability to bind specifically to LFA-1, it may act to regulate cell adhesion by promoting de-adhesion. Alternatively, cICAM-1 may be the indirect consequence of inflammation or tissue damage. As such, the detection of cICAM-1 could be useful as a marker of inflammatory disease.

High titers of cytopathic virus in plasma of patients with symptomatic primary HIV-1 infection.

Abstract: Background. Primary infection with the human immunodeficiency virus (HIV-1) frequently causes an acute, self-limited viral syndrome. To examine the relations among viral replication, the immune response of the host, and clinical illness during this initial phase of infection, we undertook a quantitative, molecular, and biologic analysis of infectious HIV-1 in the blood and plasma of three patients with symptomatic primary infection and of a sexual partner of one of them. Methods. During an eight-week period of primary infection, HIV-1 was cultured frequently in dilutions of plasma and peripheral-blood mononuclear cells (PBMC), and levels of HIV-1 antigen and antibody were determined sequentially by enzyme-linked immunosorbent assay and immunoblotting. Replication-competent HIV-1 proviruses were cloned and characterized biologically. Results. Six to 15 days after the onset of symptoms, high titers of infectious HIV-1 (from 10 to 103 tissue-culture—infective doses per milliliter of plasma) and vira...

Normal development and function of CD8+ cells but markedly decreased helper cell activity in mice lacking CD4.

Abstract: T CELLS express T-cell antigen receptors (TCR) for the recognition of antigen in conjunction with the products of the major histocompatibility complex1,2. They also express two key surface coreceptors, CD4 and CDS, which are involved in the interaction with their ligands3,4. As CD4 is expressed on the early haemopoietic progenitor5 as well as the early thymic precursor cells6, a role for CD4 in haemopoiesis and T-cell development is implicated. Thymocytes undergo a series of differentiation7 and selection steps8,9 to become mature CD4+8− or CD4−8+ (single positive) T cells10,11. Studies of the role of CD4+ T cells in vivo have been based on adoptive transfer of selected or depleted lymphocytes, or in vivo treatment of thymectomized mice with monoclonal antibodies causing depletion of CD4+ T cells12–14. In order to study the role of the CD4 molecule in the development and function of lymphocytes, we have disrupted the CD4 gene in embryonic stem cells15–16 by homologous recombination17–18. Germ-line transmission19–20 of the mutation produces mutant mouse strains that do not express CD4 on the cell surface. In these mice, the development of CD8+ T cells and myeloid components is unaltered, indicating that expression of CD4 on progenitor cells and CD4+ CD8+ (double positive) thymocytes is not obligatory. Here we report that these mice have markedly decreased helper cell activity for antibody responses, although cytotoxic T-cell activity against viruses is in the normal range. This differential requirement for CD4+ helper T cells is important to our understanding of immune disorders, including AIDS, in which CD4+ cells are reduced or absent.

Elimination from peripheral lymphoid tissues of self-reactive B lymphocytes recognizing membrane-bound antigens.

Abstract: The long-standing hypothesis that tolerance to self antigens is mediated by either elimination or functional inactivation (anergy) or self-reactive lymphocytes is now accepted, but little is known about the factors responsible for initiating one process rather than the other. In the B-cell lineage, tolerant self-reactive cells persist in the peripheral lymphoid organs of transgenic mice expressing lysozyme and anti-lysozyme immunoglobulin genes, but are eliminated in similar transgenic mice expressing anti-major histocompatibility complex immunoglobulin genes. By modifying the structure of the lysozyme transgene and the isotype of the anti-lysozyme immunoglobulin genes, we demonstrate here that induction of anergy or deletion is not due to differences in antibody affinity or isotype, but to recognition of monomeric or oligomeric soluble antigen versus highly multivalent membrane-bound antigen. Our findings indicate that the degree of receptor crosslinking can have qualitatively distinct signalling consequences for lymphocyte development.