The roles of gammadelta T cells in host defense aginst bacterial infection

T细胞通过由α链和β链组成的T细胞受体（TcR）在自身mhc抗原的背景下识别名义抗原。另一种由γ链和δ链组成的TcR也被发现。据报道，至少有相当一部分γ / δ T细胞专门识别分枝杆菌抗原上的表位，这表明携带γ / δ的T细胞可能参与抵抗各种病原体入侵的免疫监视。为了阐明γ / δ T细胞在宿主防御细菌感染中的潜在作用，我们检测了γ / δ T细胞及其配体在单核增生李斯特菌、霍乱沙门氏菌和卡介苗腹腔感染过程中的动力学。在感染这种细胞内细菌时，特异性为65kd hsp的TcR γ / δ T细胞在外观上先于特异性为细菌抗原的TcR α / β T细胞。γ / δ T细胞通过识别感染细胞上的外源性和内源性65kd热敏蛋白并产生细胞因子（如gammaIFN），为抵抗感染提供了第一道防线。我们的研究结果表明，在抗原特异性α / β T细胞克隆扩增之前，hsp特异性γ / δ T细胞对抗原多样性病原体的反应很快，它们在吞噬系统和由α / β T细胞介导的高度进化的免疫反应之间起着覆盖作用。

T cells recognize nominal antigens in the context of self-MHC antigens by T cell receptor(TcR) which is composed of alpha and beta chains. Another type of TcR, which is composed of gamma and delta chains has also identified. At least a significant fraction of gamma/delta T cells are reported to be specialized to recognize epitopes on mycobacterial antigens, suggesting that the gamma/delta bearing T cells may participate in immune surveillance against invasion with the various pathogens.To elucidate a potential role of the gamma/delta T cells in host-defense against bacterial infection,we examined the kinetics of gamma/delta T cells and their ligands during intraperitoneal infections with Listeria monocytogenes, Salmonella chorelaesuis and BCG.During infection with such intracellular bacteria, TcR gamma/delta T cells specific for 65kd hsp precede TcR alpha/beta T cells specific for bacterial antigens in appearance. The gamma/delta T cells provide a first line of defense against the infection by recognizing exogenous and endogenous 65 kd hsp on infected cells and producing cytokines such as gammaIFN. Our results suggest that the hsp- specific gamma/delta T cells respond quickly to antigenically diverse pathogens before antigen-specific alpha/beta T cells expand clonally, and they play a role in covering the gap between the phagocytic system and highly evolved immune response mediated by alpha/beta T cells.