Foulis A K
J Pathol. 1986 Sep;150(1):5-11. doi: 10.1002/path.1711500103.
T helper lymphocytes only recognize the antigen to which they are directed if it is 'presented' to them by a cell expressing the same class II major histocompatibility complex (MHC) antigen as themselves. Since the target cells of most organ specific autoimmune diseases do not normally express class II MHC proteins on their surface, any cell specific surface antigens they possess may never have been presented, and therefore immunological tolerance to them may not exist. The target cells in several organ specific autoimmune diseases have been shown to express class II MHC aberrantly and this expression may have allowed presentation of such cell specific surface antigens to potentially autoreactive T helper lymphocytes. It has therefore been proposed that aberrant expression of class II MHC antigens may be an initiating factor in certain autoimmune diseases.
辅助性T淋巴细胞只有在抗原由表达与自身相同的II类主要组织相容性复合体（MHC）抗原的细胞“呈递”给它们时，才会识别该抗原。由于大多数器官特异性自身免疫性疾病的靶细胞通常不在其表面表达II类MHC蛋白，它们所拥有的任何细胞特异性表面抗原可能从未被呈递过，因此对这些抗原的免疫耐受性可能不存在。在几种器官特异性自身免疫性疾病中，靶细胞已被证明异常表达II类MHC，这种表达可能使得此类细胞特异性表面抗原呈递给潜在的自身反应性辅助性T淋巴细胞。因此，有人提出II类MHC抗原的异常表达可能是某些自身免疫性疾病的起始因素。
