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当T细胞受体识别另一细胞表面的抗原决定簇时即被激发产生应答。近来的研究表明,在某些条件下,T细胞自身被另一T细胞识别后,被识别的T细胞能被激发而灭活识别它的T细胞(图1)。这种现象叫做“否决现象”(Veto Phenomenon),具有这一功能的细胞叫做“否决细胞”(Veto Cell)。至少某些T细胞具有这一功能。如图1所示,T细胞识别否决细胞后(箭头①),被否决细胞灭活(箭头②)。否决机制的特异性决定于否决细胞表面的抗原决定簇而不决定于其所带的受体。资料表明,否决现象在自身免疫耐受的维持与免疫应答的负向调节中可能起着重要作用,
T-cell receptors are provoked when they recognize an antigenic determinant on the surface of another cell. Recent studies have shown that under certain conditions, after T cells recognize themselves by another T cell, the recognized T cells can be activated to inactivate T cells that recognize it (FIG. 1). This phenomenon is called the Veto Phenomenon, and the cell with this function is called the Veto Cell. At least some T cells have this function. As shown in Figure 1, T cells recognize reject cells (arrow ①) and are rejected by rejected cells (arrow ②). The specificity of a rejection mechanism depends on rejecting epitopes on the surface of the cell and not on the receptors they carry. The data show that the phenomenon of rejection may play an important role in the maintenance of autoimmune tolerance and the negative regulation of immune response,