Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026918 (Mycobacterium)
 52,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The phenotype of inflammatory cells in lymph nodes from 16 patients with culture-proven tuberculous lymphadenitis were examined by histological and immunohistochemical techniques. Eight patients were suffering from a symptomatic HIV1 infection and 8 patients were immunocompetent individuals without positive HIV1 serology. In addition, the lymph nodes of 2 AIDS patients with Mycobacterium avium-intracellulare infection were examined using the same techniques. Characteristic granulomas with or without caseation were observed in the 8 immunocompetent and the 4 HIV1-infected patients with less marked lymphopenia of CD4+ peripheral blood lymphocytes (PBL). In lymph nodes from the other HIV1-infected patients with more severe depression of CD4+ PBL, no epithelioid cell formation was present; instead, foamy macrophages were found. The phenotype of the macrophages underwent progressive changes in parallel with the decreasing numbers of CD4+ PBL. Foamy macrophages in M. avium-intracellulare infection exhibited remarkable erythrophagocytotic activity and may represent an end-stage phenotype. They were positive for S100 protein and did not produce lysozyme or alpha-1-antichymotrypsin. They lost the antigen which was detected by monoclonal antibody Mac387 whereas positivity for HLA-DR, CD68 and KI-M8 was preserved. While many lymphocytes expressed CD25 (IL2 receptor) in cases with typical granulomas, there was no such CD25 expression in cases without epithelioid cell formation. Although granulomas have been produced in experimental animals independently of cell-mediated immune mechanisms, our results suggest that T-cell functions are necessary for epithelioid granuloma formation in human tuberculosis.
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PMID:In situ immunophenotype of macrophages and lymphocytes in granuloma formation of tuberculous lymphadenitis in HIV-infected and immunocompetent patients. 189 41

Genetic control of immune response was investigated by family and population analyses in humans. It was first recognized that there are high responders and low or non responders to natural antigens in human population. Family analysis revealed that low responsiveness to streptococcal cell wall antigen (SCW) was inherited as an HLA-linked dominant trait. CD8+ suppressor T cells existed in low responders and depletion of the CD8+ T cells from low responders could restore the strong immune response to SCW. Therefore the gene controlling the low response to SCW was designated as an immune suppression gene for SCW. Immune suppression gene for SCW was in strong linkage disequilibrium with particular alleles of HLA-DQ locus. The association between HLA-DQ alleles and low responsiveness mediated by CD8+ suppressor T cell was also observed for schistosomal antigen, Mycobacterium leprae antigen, tetanus toxoid, cryptomeria pollen antigen and hepatitis B virus surface antigen suggesting that low responsiveness to those antigens was also controlled by immune suppression genes. Anti-HLA-DR monoclonal antibodies inhibited the immune response to those antigens of high responders in vitro, but anti-HLA-DQ monoclonal antibodies did not. On the other hand, anti-HLA-DQ monoclonal antibodies restored the immune response in low responders. Therefore, it is suggested that HLA-DR upregulates immune response and that HLA-DQ downregulates it and that HLA-DQ is epistatic to HLA-DR in the regulation of immune response in humans. Furthermore, direct evidence for the differential in immune regulation between HLA-DR and DQ was obtained by analyzing the SCW specific T cell lines from low responders. SCW specific and HLA-DQ restricted CD4+ T cell lines could activate CD8+ suppressor T cells which in turn downregulate SCW specific CD4+ T cells whereas SCW specific and HLA-DR restricted CD4+ T cell lines could not activate CD8+ suppressor T cells. All these observation clearly demonstrated that the HLA-linked immune suppression genes exist in humans to control low response to natural antigens.
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PMID:HLA-linked immune suppression genes. 214 11

Previously we showed that certain T cell lines and clones from a lepromatous leprosy patient displayed a dose-dependent suppression of the proliferation of autologous T cells to Mycobacterium leprae (M. leprae) but not mitogen or an unrelated antigen. The latter cells were also cloned and did not display this suppressive activity, were CD4+ and proliferated vigorously to M. leprae presented by autologous HLA-DR molecules. We shall refer to these cells as T helper (Th) cells. Most of the suppressive T cell clones (Ts) were also CD4+ and also proliferated to M. leprae presented by HLA-DR, but much less strongly than Th cells. In this study we report on our search for (a) the mechanism of this apparently antigen-specific suppression by T cells, and (b) a possible phenotypic difference between Th and Ts clones. The two main conclusions are that Ts clones possess a lytic machinery, but that M. leprae-specific suppression and cytotoxicity can be clearly dissociated, and that the only phenotypic difference between Th and Ts is the presence of the CD28 marker on Th and its absence on Ts clones.
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PMID:Human suppressor T cell clones lack CD28. 216 78

Immunosuppressive mechanisms loom as important factors in depression of delayed-type hypersensitivity responses during active tuberculosis. Nonspecific suppression may be mediated by circulating immune complexes containing mycobacterial polysaccharides such as D-arabino-D-galactan. The mechanism of suppression involves activation of monocyte production of immunosuppressive prostaglandin E2. Peripheral blood mononuclear cells from patients with tuberculosis include increased numbers of monocytes that suppress the response to tuberculin purified protein derivative (PPD). Antigen-specific suppression is associated with monocyte activation by a number of criteria, including decreased surface expression of HLA-DR determinants and increased production of interleukin 1 (IL-1). The increased production of IL-1 is associated with--and may have a causal relation to--immunosuppression. A second parallel regulatory mechanism involves PPD-specific suppression by Fc gamma receptor-bearing lymphocytes. The consequence of these immunosuppressive circuits is depression of tuberculin-induced blastogenesis, production of IL-2, and generation of IL-2 receptors. These findings suggest that natural infection with Mycobacterium tuberculosis may result in immunosuppression. Studies of potentially protective antigens in experimental systems must be designed to assess and avoid activation of suppressor circuits.
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PMID:Immunologic aspects of mycobacterial infections. 246 22

Studies in experimental animals have demonstrated that the T cell response to immunogenic proteins is limited to one or a few epitopes on such proteins and that the MHC haplotype of the responder is an important factor in determining which epitope is recognized (immune response gene effect). However, if and to what extent MHC genes control the immune response to pathogens in man is virtually unknown. We have studied the human T cell response to the mycobacterial 65-kDa heat-shock protein, a major immunogen of Mycobacterium leprae and M. tuberculosis, the causative agents of leprosy and tuberculosis, respectively, in relation to HLA-DR phenotype. In a large panel of short-term cultured polyclonal anti-mycobacterial T cell lines, from 45 different individuals representing all DR-restriction specificities, only DR1 and DR3-restricted T cell lines proliferated to the 65-kDa protein. The DR1-restricted T cell lines responded to three new epitopes on the mycobacterial 65-kDa protein, one of which is specific for the M. tuberculosis complex. Altogether nine T cell epitope-containing regions have now been mapped on the 65-kDa protein and the response to each of them was exclusively restricted via one HLA-DR allele. Most importantly, all six 65-kDa-responsive DR3-restricted T cell lines from different individuals recognized an epitope on the same peptide, representing amino acids 2-12 of the 65-kDa protein, that was previously mapped using DR3-restricted T cell clones. From these data we conclude that the human T cell response to both the whole mycobacterial 65-kDa heat-shock protein and to defined epitopes on this protein is controlled by HLA-DR genes. The mycobacterial 65-kDa protein has been implicated in the design of subunit vaccines against tuberculosis and leprosy as well as the induction of immunopathology. In both instances the Ir gene control of the T cell response to this protein may have to be taken into account.
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PMID:DR3-restricted T cells from different HLA-DR3-positive individuals recognize the same peptide (amino acids 2-12) of the mycobacterial 65-kDa heat-shock protein. 248 Sep 2

There is no doubt that HLA-DR molecules are acting as the products of HLA-linked immune response genes (Ir-genes), because (i) HLA-DR molecules are the restriction elements in the interaction between CD4+ helper T cells and antigen-presenting cells (APC) to respond to many antigens such as streptococcal cell wall antigen (SCW) (Nishimura & Sasazuki, 1983; Sone et al., 1985; Hizayama et al., 1986), schistosomal antigen (Sj) (Hirayama et al., 1987), Mycobacterium leprae antigen (ML) (Kikuchi et al., 1986) and so on; and (ii) anti-HLA-DR monoclonal antibodies completely abolish the immune response to those antigens (Nishimura & Sasazuki, 1983; Sone et al., 1985). However, genetic analysis of the immune response to those antigens in families or populations revealed that responsiveness is recessive and non-responsiveness to those antigens is a dominant genetic trait that is tightly linked to HLA (Sasazuki et al., 1980a, 1983; Watanabe et al., 1988). This is completely opposite to the situation under the Ir-gene control where responsiveness is dominant and non-responsiveness is recessive. In this paper, we report evidence of how we came across the concept of HLA-linked immune suppression genes (Is-genes) besides Ir-genes, and show evidence for the epistatic interaction between HLA-DR and DQ to determine the immune response to several antigens in humans.
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PMID:HLA-linked immune suppression in humans. 250 34

The immune response to mycobacterial pathogens comprises a significant percentage of T cells with specificity for a 65-kDa heat shock protein (hsp) which is highly conserved in bacteria and man. PBMC were activated in vitro with killed Mycobacterium tuberculosis and afterward tested for CTL activity on autologous target cells primed with 1) killed M. tuberculosis, 2) intact recombinant 65-kDa hsp of Mycobacterium bovis/M. tuberculosis; or 3) tryptic fragments of the recombinant 65-kDa hsp. Strong CTL activity was observed on targets primed with killed M. tuberculosis or with tryptic fragments of the 65-kDa hsp, but not on those primed with the intact 65-kDa hsp. M. tuberculosis activated T cells from 2/13 donors tested exerted killer activity against unprimed targets. To assess whether T cell responses were directed against self-epitopes shared by the mycobacterial and human 65-kDa hsp, four peptides of at least 10 amino acids length were synthesized corresponding to fully or almost identical regions of these molecules. Peripheral blood T cells from 8/9 individuals tested, after activation with killed M. tuberculosis, expressed strong CTL activity toward autologous targets primed with one or more of these synthetic peptides. By using HLA-DR transfected murine L cells we found that the epitopes were recognized in the context of histocompatible HLA-DR (class II) molecules. We conclude that the demonstration of T cells with specificity to self-epitopes in vitro is not indicative for autoimmune disease. However, if at certain stages of infection such T cells are activated by crossreactive microbial epitopes they could cause autoimmune responses.
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PMID:T lymphocytes from healthy individuals with specificity to self-epitopes shared by the mycobacterial and human 65-kilodalton heat shock protein. 250 58

The outcome of an infection with Mycobacterium leprae is correlated with the T-cell-mediated immune response developed against this pathogenic agent. The identification of M. leprae antigens that are recognized by T cells is therefore of great importance. In this paper we present the results of in vitro lymphoproliferation assays in which T-cell reactivity was measured against a peptidoglycan-protein complex (PPC) which was purified from the cell wall of M. leprae. Twelve M. leprae-reactive T-cell clones with different antigen specificities from a tuberculoid (TT) leprosy patient showed proliferative responses, but only when PPC was presented by HLA-DR-matched antigen-presenting cells (APCs). Four of these clones were known to react with the recombinant mycobacterial 65-kDa protein. A tetanus-toxoid-reactive T-cell line from a healthy control was not stimulated by this complex, supporting the idea that the stimulation by PPC was antigen specific. Both PPD-reactive and M. leprae-reactive T-cell lines from healthy individuals were stimulated by PPC. However, when this complex was presented to PPD-reactive T-cell lines derived from two lepromatous (LL) leprosy patients, we did not observe any proliferative responses. From these results we conclude that PPC contains most or all of the antigens which stimulate M. leprae-reactive T cells in association with relevant HLA class II molecules, including the 65-kDa protein or at least some immunogenic parts of it.
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PMID:A peptidoglycan protein complex purified from M. leprae cell walls contains most or all immunodominant M. leprae T-cell antigens. 268 61

HLA-DR and -DQ restriction fragment length polymorphisms (RFLPs) were examined in Melanesian leprosy patients and controls from New Caledonia. This permitted DNA subtyping of DQw1, a broad serological specificity previously implicated in predisposition to lepromatous leprosy. The DQw1c subtype, found in linkage disequilibrium with DR1, w10, w14, and some Pacific Island variants of DRw6 and DRw8, was significantly reduced in leprosy patients. Since the association between HLA-DR genes and leprosy is not strong, some candidate non-MHC genes for leprosy susceptibility were examined also. T-cell receptor -alpha, -beta, and -gamma gene RFLPs revealed no germ-line defects or major clonal T-cell expansion in either lepromatous or tuberculoid leprosy patients. The human homologue of the murine Ity locus which determines murine susceptibility to Mycobacterium lepraemurium was sought by examining linkage disequilibrium with RFLPs in the human gamma-crystallin genes, since this gene family forms a syntenic group with isocitrate dehydrogenase-1 in both mouse and man and, in the mouse, this cluster is closely linked to the Ity locus. These RFLPs were not associated with leprosy susceptibility in man.
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PMID:HLA-DR, -DQ DNA genotyping and T-cell receptor RFLPs in leprosy. 290 35

This paper reviews the rationale and history of genetic studies related to leprosy, and considers their implications for the epidemiology and control of the disease. A long tradition of genetic studies in leprosy was initiated by early impressions that the disease clusters within families. Investigations were first motivated by an attempt to understand population patterns, and the focus shifted from investigations of racial differences to investigations of families, of twins and ultimately of genetic markers. The strongest evidence for genetic influence has come from studies of HLA segregation patterns within families, and this has led to elegant in vitro work demonstrating the role of HLA-DR alleles in mediating T-cell reactions in conjunction with antigens of Mycobacterium leprae. The epidemiological implications of this work are not yet clear. The emphasis on family-segregation studies may have given a biased impression because of their requirement for multi-case families. There is evidence that the genetic mechanisms underlying leprosy differ within and between populations. One possible application of the current work would be the use of HLA-DR-specific reactions to identify epitopes of M. leprae which should be excluded from future vaccine preparations.
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PMID:Implications of genetics for the epidemiology and control of leprosy. 290 49


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