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Query: UMLS:C0153470 (Spleen)
 4,015 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in the antigenicity of major histocompatibility complex (MHC) class I molecules resulting from the association of bovine beta 2-microglobulin (beta 2-m) with mouse class I heavy chains were investigated. Mice (H-2b) were immunized with syngeneic Concanavalin A (Con A) blasts induced in the presence of fetal calf serum (FCS) in conditions allowing exchange between mouse and bovine beta 2-microglobulin (beta 2-m). Spleen cells from hyperimmunized mice were fused with myeloma cells and two monoclonal antibodies which required for their reactivity the presence of FCS have been further studied. One of them (CAB 297) recognized a determinant of bovine beta 2-m which is present on free molecules in solution as well as when they are associated with either mouse or bovine class I heavy chains. In contrast, the second monoclonal antibody (CBB 70) did not react with free bovine beta 2-m molecules, nor with beta 2-m associated with bovine class I heavy chains. It did react with cells of some H-2 haplotypes (b, f, p and r) but only when their class I heavy chains are associated with bovine or with human beta 2-m. Therefore, expression of the CBB 70 defined antigenic determinant requires both xenogeneic beta 2-m and class I heavy chain of a given H-2 molecule. In order to precisely localize the antigenic determinant defined by this monoclonal antibody and therefore the region altered by the association of class I heavy chain with xenogeneic beta 2-m, we made use of exon shuffled class I molecules. The results indicate that changes induced by the association of bovine beta 2-m with H-2 class I heavy chain affect the conformation of the alpha 2 domain. These studies illustrate that MHC class I molecules exhibit a considerable conformational flexibility which could influence their ability to bind and present various peptides to the T-cell receptor.
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PMID:Localization of the conformational alteration of MHC molecules induced by the association of mouse class I heavy chain with a xenogeneic beta 2-microglobulin. 137 66

We have investigated the ability of various antigen-presenting cell (APC) types to induce primary anti-viral cytotoxic T lymphocyte (CTL) responses by single in vitro stimulation. Of these APC types, only dendritic cells (DC) and RMA-S lymphoma cells could induce primary CTL responses, but by divergent mechanisms. DC were capable of generating primary virus-specific CTL, either by presenting viral peptide or processed infectious virus. In contrast, RMA-S cells could not present endogenous antigen, e.g. after virus infection, but this cell line very efficiently presented exogenous viral peptides to induce primary virus-specific CTL in vitro. Spleen cells, lipopolysaccharide-induced B cell blasts or the non-mutated RMA cells did not have the ability to trigger unprimed T cells by single in vitro stimulation. We have investigated several characteristics important for primary CTL response induction by DC and RMA-S cells (summarized in Fig. 6). Primary CTL response induction by DC or RMA-S cells was blocked by anti-LFA-1 or anti-CD8 monoclonal antibodies (mAb). DC rapidly aggregated with unprimed T cells, which was independent of LFA-1 and CD8 molecules. RMA-S cells did not form conjugates with unprimed T cells. Despite their abundant major histocompatibility complex (MHC) class I cell-surface expression, DC did not bind much exogenously added viral peptide. In contrast, the MHC class I molecules on RMA-S cells bound a large quantity of exogenously administered peptide. Powerful adhesion by DC and high expression of relevant MHC/peptide complexes on RMA-S cells are important features in the initial contact with unprimed T lymphocytes. In a later stage of contact, both DC and RMA-S cells activate LFA-1 (and CD8) molecules at the T cell surface to strengthen and maintain the contact between T cell and APC.
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PMID:Mechanisms of induction of primary virus-specific cytotoxic T lymphocyte responses. 142 25

The role of major histocompatibility complex (MHC) class I expression in natural killer (NK) cell target recognition is controversial. Normal T cell blasts from MHC class I-deficient mutant mice were found to serve as target cells for NK cells in vitro, which suggests that MHC class I molecules are directly involved in NK cell recognition. Spleen cells from the mutant mice were deficient in their ability to lyse MHC class I-deficient target cells or NK-susceptible tumor targets, and mutant mice could not reject allogeneic bone marrow. Thus, class I molecules may participate in the positive selection or tolerance induction of NK cells.
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PMID:MHC class I deficiency: susceptibility to natural killer (NK) cells and impaired NK activity. 185 5

T cell immune responses in syngeneic WKA/H rats were analyzed by using lymphoid cell lines, TARS-1, TART-1, and TARL-2, infected with human T-lymphotropic virus type 1 (HTLV-1). Spleen cells of rats in which these cell lines had been rejected were sensitized in vitro with the same cell lines, and cells cytotoxic to these HTLV-1+ cell lines, and cells cytotoxic to these HTLV-1+ cell lines were generated. The effector cells were CTL of the CD5+ CD8+ phenotype and showed restriction of MHC class I Ag. Direct tests as well as cold target cell inhibition tests with an array of cell populations showed that these CTL reacted only with syngeneic HTLV-1+ cell lines. When xenogeneic HTLV-1+ cell lines were similarly utilized for in vitro sensitization, rat CTL specific for syngeneic HTLV-1+ cells were generated. They were not, however, reactive with xenogeneic HTLV-1+ cells used for sensitization. Syngeneic rat cells selectively expressing gag, env, or pX gene coded Ag were prepared by infection of recombinant vaccinia viruses. In cold target cell inhibition tests of anti-HTLV-1 CTL with thus prepared cells, cytotoxicity against the syngeneic HTLV-1+ cells line, TARS-1, was inhibited by syngeneic cells expressing gag gene or env gene coded Ag. Inhibition was, however, more consistent and more dominant by cells with gag gene than those with env gene. Syngeneic cells with pX gene and MHC class I incompatible cells with gag, env, or pX gene did not inhibit cytotoxicity.
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PMID:Rat cytotoxic T lymphocytes against human T-lymphotropic virus type 1-infected cells recognize gag gene and env gene encoded antigens. 247 89

The non-obese diabetic (NOD) mouse is an animal model of insulin-dependent diabetes mellitus (IDDM), in which 80% of the females become diabetic after the age of 12 weeks. Using an in vitro assay we investigated the capacity of spleen lymphocytes from NOD mice to inhibit the insulin secretion of normal islet cells after stimulation by theophylline plus arginine. Spleen cells from diabetic NOD mice inhibited the insulin release of DBA/2 islet cells. Depletion experiments using monoclonal antibodies demonstrated that inhibitory cells belonged to the Lyt2 positive T lymphocyte subset. The phenomenon was not restricted by the MHC class I K region, shared by NOD and DBA/2 mice, since lymphocytes from diabetic NOD mice also inhibited the insulin secretion of normal Wistar rat islet cells. Inhibitory T cells were detected in overtly diabetic mice but also in non-diabetic females aged 5-11 weeks indicating that they are not secondary to metabolic disturbances and might contribute to their onset. Conversely they were not found in male NOD mice although some of these mice show insulitis. The presence of these inhibitory T cells might thus represent an early and sensitive marker of anti-islet cell-mediated autoimmunity.
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PMID:Cell-mediated immunity to pancreatic islet cells in the non-obese diabetic (NOD) mouse: in vitro characterization and time course study. 305 43

CD8+ T lymphocytes have been reported to play a major role in the protective immune response against acute infection with Toxoplasma gondii. In order to further assess the role of CD8+ cells in resistance against this protozoan we examined the ability of beta 2m-deficient mice, which fail to express MHC class I molecules and peripheral CD8+ lymphocytes, to survive tachyzoite challenge following vaccination with an attenuated parasite mutant. Surprisingly, vaccination of beta 2m-deficient mice induced strong resistance to lethal challenge, with > 50% surviving beyond 3 months. Vaccinated beta 2m-deficient mice, but not control heterozygotes, showed a five- to six-fold expansion in spleen cell number and approximately 40% of the splenocytes were found to express the NK markers NK1.1 and asialo GM1. Spleen cells from the vaccinated beta 2m-deficient animals failed to kill either infected host cells or the NK target YAC-1. However, high levels of IFN-gamma were secreted when the cells were cultured in vitro with soluble T. gondii lysate, and this response was abolished by NK1.1+ but not CD4+ and CD8+ lymphocyte depletion, implicating the NK1.1+ population as the major source of IFN-gamma. More importantly, vaccine-induced immunity in beta 2m-deficient mice was completely abrogated by in vivo administration of antibody to NK1.1, asialo GM1, or IFN-gamma. Together, the data suggest that in class I-deficient mice vaccinated against T. gondii, the absence of CD8+ effector cells is compensated for by the emergence of a population of NK1.1+ and asialo GM1+ cells which lack cytolytic activity, and that the protective action of these cells against the parasite is attributable to IFN-gamma production. The induction of this novel NK population may provide an approach for controlling opportunistic infections in immunocompromised hosts.
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PMID:Emergence of NK1.1+ cells as effectors of IFN-gamma dependent immunity to Toxoplasma gondii in MHC class I-deficient mice. 822

Reactive arthritis (ReA) due to Gram-negative intestinal bacteria or Chlamydia, is associated by an unknown mechanism with HLA-B27. Like other MHC class I molecules, HLA-B27 presents antigenic peptides derived from intracellular proteins to CD8+ cytotoxic T cells (CTL). In humans however, CTL specific for ReA associated bacteria have been reported in a limited number of studies. This may be caused by an inefficient in vivo induction of CTL against such micro-organisms. In the present study we addressed the question whether and to what extend mice transgenic for HLA-B27 are able to generate CTL against Salmonella typhimurium after immunization. To this end both HLA-B27 transgenic and non transgenic mice were immunized i.p., i.v. or orally, receiving a secondary challenge four weeks later. One day after infection with Salmonella, bacteria could be cultured from spleen and liver. There was no significant difference in the number of bacteria cultured from these organs between both groups of mice. Spleen cells from all immunized mice proliferated specifically in the presence of heat killed Salmonella but not in the presence of heat killed Yersinia. No proliferation of spleen cells from naive mice was observed in the presence of heat killed Salmonella, excluding the possibility that Salmonella antigens were mitogenic. Only in one out of 6 mice immunized i.v. with Salmonella Salmonella specific CTL could be generated. In order to rule out the possibility that in HLA-B27 transgenic mice the HLA-B27 molecule is not used as a restriction element by murine T cells, CTL were raised against the male minor histocompatibility (mH) antigen H-Y. Both murine class I as well as HLA-B27 restricted CTL could be generated. In conclusion this study demonstrates that MHC class I restricted CTL specific for the Gram-negative bacterium Salmonella typhimurium are difficult to generate in contrast to proliferative responses which can be easily demonstrated. This may comparable in humans where in the majority of studies bacteria specific T cells isolated from ReA patients appear to be CD4+ and class II restricted.
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PMID:Immunization of HLA-B27 transgenic and non transgenic mice with Salmonella typhimurium results predominantly in the generation of proliferative T cell responses. 883 10

In this paper, we examined the induction of autoimmune-like histologic changes in the liver and other organs of mice undergoing graft-versus-host reaction (GVHR) with MHC class I disparity by the administration of bacterial lipopolysaccharide (LPS), on the assumption that stimulation with LPS could be an exacerbating factor. Spleen cells of C57BL/6 (B6) mice were injected twice into (B6 x bml) F1 recipient mice at an interval of 7 days to induce MHC class I GVHR and then challenged with 1 microg of LPS intravenously on the next day of the cell transfer. The hepatic lesions of the group of MHC class I GVHR mice challenged with LPS showed marked cellular infiltration at the portal area and focal necrosis was observed in the hepatic lobule. The major infiltrating cells were CD8+, and others including CD4+ cells being of minor populations. In addition, ductal lesions in extrahepatic organs, including the pancreas and salivary glands also showed marked cellular infiltration. Thus, we have demonstrated that LPS induced ductal lesions in mice with MHC class I disparity. CD8+ cells were detected at the destructive hepatic lesions, which might be effector cells. These findings indicate that LPS might be one of the potential factors which augment autoimmune-like lesions.
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PMID:Induction of autoimmune-like hepatic and ductal lesions by administration of lipopolysaccharide in mice undergoing graft-versus-host reaction across MHC class I difference. 941 23

Initiation of an Ab response requires interaction between dendritic cells (DC), T cells, and B cells in a T cell area. We demonstrate that rat DC and B cells form T cell-independent clusters in vitro and in vivo. In vitro clusters form within 1 h and dissociate within 24 to 48 h. Clustering is restricted to resting B cells, is energy, cytoskeleton, and protein kinase C dependent, and is inhibited by anti-LFA-1 but not anti-ICAM-1 mAbs. Spleen and lymph node B cells cluster more strongly than those from lymph or blood, suggesting up-regulation of adhesiveness during transendothelial migration. Bone marrow B cells do not form clusters. DC from spleen and lymph nodes show the most clustering, lymph-borne DC are intermediate, and DC from lamina propria, Peyer's patches, and those grown from bone marrow form the fewest clusters. Clustering is stimulated by cross-linking MHC class II (whole mAb or F(ab')2) on DC or B cells or Thy-1 on DC, but not MHC class I, CD45, or CD44. Stimulation by mAb is energy, cytoskeletal, and protein kinase C dependent, but is not inhibited by anti-LFA-1 mAbs, suggesting involvement of other, unidentified adhesion molecules. We suggest that interactions between DC and B cells will occur regularly during B cell recirculation. Cross-linking of MHC class II-peptide molecules on DC by specific T cells would increase binding avidity, causing retention of Ag-specific B cells on DC long enough for the B cells to process Ag, thereby facilitating cognate interactions between T and B cells.
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PMID:Dendritic cells and resting B cells form clusters in vitro and in vivo: T cell independence, partial LFA-1 dependence, and regulation by cross-linking surface molecules. 946 36

Hepatitis C Virus (HCV) causes most cases of posttransfusion hepatitis. Chronic HCV infection is highly related to chronic hepatitis, cirrhosis and hepatocellular carcinoma. Current therapies are only minimally effective and no vaccine has been developed. DNA-based immunization could be of prophylactic and therapeutic value for HCV infection. By intramuscular inoculation in BALB/c mice with an HCV recombinant plasmid pCI-HCV-C, we found significant levels of IgM antibody, but no significant IgG rise. After boost the immunized mice with recombinant HCV-core protein (cp1-10; 1-164aa), the anticore IgG, verified by Western-blotting, rose rapidly, which was two weeks earlier than that with control plasmid. Spleen cells from pCI-HCV-C immunized mice gave higher proliferation index (PI) than control (P < 0.05). The PI of cp1-10 boosted mice was even higher. Proliferation blocking assay with mAb proved the responding cell to be of CD4+ CD8- phenotype, supporting specific priming of T helper cells. A 51Cr-releasing CTL assay specific for HCV-core was developed, and a specific CTL response against HCV-core was demonstrated in both pCI-HCV-C immunized mice and mice boosted with cp1-10. Strong cytotoxic activity against peptide-pulsed p815 cells (H-2d), but not EL-4 cells (H-2b), suggested MHC class I restriction of the CTL activity. Blocking of CTL with mAb proved the effector cells to be of CD4- CD8+. Three CTL epitopes in HCV-core protein were demonstrated. We failed to detect CTL when immunized only with core protein. The results suggested that vaccination with HCV-core derived DNA sequences could be an effective method to induce humoral and cellular immune responses to HCV.
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PMID:Characterization of the humoral and cellular immune responses against hepatitis C virus core induced by DNA-based immunization. 1046 52


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