[CD4-CD8- to CD4-CD8+ transition induced by anti-CD3 mAb in vitro cell culture system]

In our experiments, we have observed the effect of anti-CD3 mAb in inducing the differentiation of CD4-CD8- (double negative, DN) thymocytes into CD4+ CD8+ (double positive, DP) cells in an in vitro cell culture system including IL-7 for maintaining the growth of TN thymocytes. When TN thymocytes were stimulated by immobilized anti-CD3 mAb for 3 days, CD4-CD8+ cells generated, which were mostly immediate precursors of CD4+CD8+ thymocytes according to their surface TCR beta expression. The transition from DN to DP thymocytes accompanied with downregulation of interleukin 2 receptor (IL-2 R) alpha chain, and the TCR alpha beta-CD3 expression induced by IL-7 was also inhibited. Anti-CD3 mAb was effective only before the appearance of functional TCR-alpha beta-CD3 complex. Taking together, the results strongly suggest that anti-CD3 mAb induced DN thymocyte defferentiation is through the pre-TCR complex.