银屑病患者外周血单一核细胞对链球菌M6蛋白的反应

目的 :探讨链球菌M6蛋白 (M 6P)在点滴型银屑病发病中的作用机制 .方法 :MTT法检测点滴型银屑病 (GP)、斑块型银屑病 (PP)患者及正常人外周血单一核细胞 (PBMC)对极微量 (10 0ng)M6P、葡萄球菌肠毒素B(staphylococcalen dotoxinB ,SEB)的增殖反应 ;双抗夹心ELISA法检测M6P刺激培养 72h点滴型银屑病PBMC上清中IFN γ,IL 4水平 .结果 :M6P可引起点滴型银屑病患者PBMC明显的增殖反应 ,与RPMI 16 4 0组 (空白对照 )差异非常显著 (P <0 .0 1) ;与斑块型组及正常对照组相比差异极显著 (P <0 .0 1) ;点滴型银屑病组M6P刺激 72h培养上清中IFN γ 含量较空白对照组明显升高 (P <0 .0 1) ,IL 4含量均未检出 .结论 :在点滴型银屑病的发病中 ,M 6P可能作为细菌超抗原刺激T细胞大量增殖后释放Th1型细胞因子而起作用     

T cells and cytokines in Crohn's disease

Recent findings indicate that activated T lymphocytes, showing restricted T-cell receptor repertoire and a Th1-like profile of cytokine production, are responsible for macrophage activation and release of inflammatory cytokines, toxic oxygen metabolites and nitric oxide, which initiate and maintain the transmural intestinal inflammation in Crohn's disease. A critical event in the promotion of Th1-type response at gut level may involve up-regulation of IL-12 production and the breakdown of tolerance against the intestinal flora.     

Treatment of PL/J mice with the superantigen, staphylococcal enterotoxin B, prevents development of experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE), an antigen induced autoimmune disease, is mediated by Vβ8⁺ CD4⁺ T cells in PL/J mice after injection with the autoantigen, myelin basic protein (MBP). Recently the superantigen, staphylococcal enterotoxin B (SEB), has been shown to peripherally anergize and delete T cells in a Vβ specific manner. By treatment of PL/J mice with SEB, we have been able to protect PL/J mice from the development of EAE. Two-color FACS analysis of the spleens of SEB treated mice showed depletion of Vβ8⁺ CD4⁺ T cells. Consistent with this observation, spleen cells of SEB treated mice that did not show signs of EAE could not be stimulated in vitro with SEB but did respond to SEA. Thus, Vβ specific superantigens may prove to be a preventive therapy for autoimmune diseases mediated by Vβ specific T lymphocytes.     

Accumulation of oligoclonal T cells in the infiltrating lymphocytes in oral lichen planus

BACKGROUND: Identification of a disease-specific and possibly pathogenic T-cell receptor (TCR) in oral lichen planus (OLP) is one of the most important steps to reveal the pathogenic antigen recognized by the T cells and thereby elucidate the pathogenesis and etiology of OLP. METHODS: In buccal mucosa biopsy specimens and peripheral blood mononuclear cells (PBMC) from seven patients with OLP, the TCR V beta gene usage was examined by polymerase chain reaction-based and single-strand conformation polymorphism analyses. RESULTS: The V beta families expressed in the biopsy specimens were markedly heterogeneous, but they were restricted in comparison to those observed in the PBMC. The V beta families predominantly expressed in the biopsy specimens in comparison with the PBMC were still heterogeneous in individual patients and differed from patient to patient; however, V beta 2, V beta 6, and V beta 19 were commonly predominant in the biopsy specimens from more than half of the patients. Among the V beta families predominantly expressed in the biopsy specimens, the accumulation of T-cell clonotypes was observed in the majority of the V beta families including V beta 6 and V beta 19; however, it was not observed in the minority of the V beta families including V beta 2. CONCLUSIONS: These results suggest that unique T-cell populations bearing V beta 2, V beta 6, or V beta 19 gene products tend to expand in OLP lesions as a consequence of in situ stimulation with a restricted epitope of either a nominal antigen on the MHC molecule for the majority of the V beta families, even if only in minor populations, or of a common superantigen for the minority of the V beta families.     

Clonal unresponsiveness results from an interaction between staphylococcal enterotoxin B and T cells expressing unexpected V beta elements.

The ability of staphylococcal toxins to stimulate large numbers of T cells has led to their designation as a superantigen. Previous studies have indicated that activation of T cells bearing particular V beta elements may be responsible for the toxic effects of these bacterial products. However, the widespread expression of functionally similar proteins by unrelated bacterial species suggests the possibility that these products may represent a successful microbial strategy for subversion of the host antibacterial response. We have examined the effects of the staphylococcal enterotoxin B (SEB) on T cell clones that express different V beta elements. We note that SEB stimulates clones bearing previously defined V beta elements to proliferate and to produce cytokines. In addition, we demonstrate that an interaction between SEB and the TCR of clones that express additional V beta elements, including V beta 2 and V beta 6, results in a sterile form of immunological activation. This activation phenotype is characterized by proliferation without detectable cytokine production and is followed by profound immunological unresponsiveness in vitro and in vivo. We propose that reduced levels of antibacterial responses resulting from this form of T cell unresponsiveness may account for the highly conserved expression of superantigens by diverse bacterial species.     

Fas (CD95) participates in peripheral T cell deletion and associated apoptosis in vivo

Following exposure to some types of antigen (superantlgens),responsive T cells expand and then decline in numbers, a phenomenonthat has been called ‘peripheral deletion’. Thisprocess may play a role in limiting autoimmune reactions andin the maintenance of immune homeostasis. Here we describe experimentson peripheral deletion in mice carrying the Ipr/lpr defect,which has been shown to be due to defective production of theCD95/Fas molecule. Young Ipr/lpr mice with no apparent Immunologlcabnormalities display a defect in bacterial superantlgen-inducedperipheral deletion. Apoptotic death of the expanded T cellpopulation associated with such peripheral deletion in normalanimals is dramatically reduced in the mutant mice. Further,the levels of Fas on responding cells in normal mice Increasesand decreases together with increases and decreases in cellnumbers, suggesting that cells with the highest levels of Fasare preferentially deleted. These observations are consistentwith the known ability of CD95 to transduce a signal leadingto apoptosis, and they implicate this signal transduction pathwayIn peripheral deletion. In contrast, bacterial superantigen-induceddeletion of thymocytes appears to be fully functional in thesemice, and thus Fas/APO-1 does not appear to be required forthis process. Further, antibody ligatlon of the TCR on activatedT cells from normal or young Ipr/lpr mice can induce apoptosisand therefore under some circumstances this phenomenon is notdependent upon CD95/Fas. Thus, to avoid autoreactivity and ensureimmune homeostasis, several different apoptotic mechanisms existIn peripheral T lymphocytes, only some of which involve Fas.Defects in one or more of these mechanisms may have profounddeleterious consequences.     

Antibody-directed superantigen-mediated T-cell killing of myeloid leukaemic cell line cells

Abstract: Bacterial superantigens (SAgs) bound to MHC class II molecules on target cells are efficient activators of cytotoxic T cells expressing certain T cell receptor (TCR) Vβ regions. We described earlier that the specificity of the SAg Staphylococcus enterotoxin A (SEA) can be changed by introducing a D227A point mutation in the major MHC class II binding site and by genetically fusing the SEA mutant (SEAm) to protein A (PA). This SEAm-PA fusion protein can then be used to direct cytotoxic T cells to tumour cells coated with monoclonal antibodies (mAbs). In this communication, we tested the PA-SEAm fusion protein together with mAbs against the myeloid cell surface antigens CD13, CD15 and CD33. A SEA-reactive T cell line was used as effector cells against 10 different myeloid leukaemic cell lines. Optimal lysis of antigen positive leukaemic cells was obtained at a PA-SEAm concentration of 1 ng/ml and effector: target cell ratios of 15 : 1. No correlation between target cell sensitivity and the level of surface antigen expression could be seen. The 6 acute myeloid leukaemia (AML) cell lines tested appeared to be more sensitive than the 4 chronic myeloid leukaemia (CML) cell lines. The sensitivity of the AML cell line HL-60 could be improved further by stimulation with TNFα. This was accompanied by increased surface ICAM-1 expression whereas specific target molecule expression (CD13, CD33) was unchanged. This suggests that sensitivity to lysis is related to the leukaemic subtype and ICAM-1 expression but not to the tumour antigen density. Our results show that it is possible to direct cytotoxic T cells to myeloid leukaemia cells by using SAgs linked to mAbs, and encourage the construction and testing of a recombinant direct SAg-mAb fusion protein as a candidate drug for therapy of myeloid leukaemias.     

Human airway and peripheral blood eosinophils enhance Th1 and Th2 cytokine secretion

BACKGROUND: The effector function of eosinophils involves their release of toxic granule proteins, reactive oxygen species, cytokines, and lipid mediators. Murine studies have demonstrated that eosinophils can also enhance T cell function. Whether human eosinophils, in particular, airway eosinophils, have similar immunoregulatory activity has not been fully investigated. The aim of this study was to determine whether human blood and airway eosinophils can contribute to Th1 and Th2 cytokine generation from CD4+ T cells stimulated with superantigen. METHODS: Eosinophils were obtained from blood or bronchoalveolar lavage fluid 48 h after segmental allergen bronchoprovocation. Purified eosinophils were co-cultured with autologous CD4+ blood T cells in the presence of staphylococcal enterotoxin B (SEB). Cytokine levels in the supernatant fluid were determined by enzyme-linked immunosorbent assay (ELISA). Eosinophil expression of major histocompatibility complex (MHC) class II and co-stimulatory molecules was assessed by flow cytometry before culture, 24 h after granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation, and 24 h after co-culture with CD4+ T cells and SEB. RESULTS: Interleukin (IL)-5, IL-13, and interferon (IFN)-gamma generation increased when CD4+ T cells were co-cultured with either blood or airway eosinophils in the presence of SEB. The ability of eosinophils to enhance cytokine generation was independent of their source (blood vs airway), activation by GM-CSF, or detectable expression of human leukocyte antigen (HLA)-DR, CD80, or CD86. CONCLUSION: Our data demonstrate that SEB-induced generation of Th1 and Th2 cytokines is increased in the presence of human blood and airway eosinophils. Thus, eosinophils can have an immunoregulatory function in pathogen-associated allergic diseases such as atopic dermatitis, chronic sinusitis, and asthma exacerbations.     

CD28: Direct and Critical Receptor for Superantigen Toxins

Every adaptive immune response requires costimulation through the B7/CD28 axis, with CD28 on T-cells functioning as principal costimulatory receptor. Staphylococcal and streptococcal superantigen toxins hyperstimulate the T-cell-mediated immune response by orders of magnitude, inducing a lethal cytokine storm. We show that to elicit an inflammatory cytokine storm and lethality, superantigens must bind directly to CD28. Blocking access of the superantigen to its CD28 receptor with peptides mimicking the contact domains in either toxin or CD28 suffices to protect mice effectively from lethal shock. Our finding that CD28 is a direct receptor of superantigen toxins broadens the scope of microbial pathogen recognition mechanisms.