Structure and biological function of human IgD. IX. Anti-IgD activation of human lymphocytes.

Human peripheral lymphocytes were stimulated to incorporate tritiated thymidine when cultured with anti-sigma. The stimulation of lymphocytes by anti-sigma inversely correlates to PHA-induced lymphocyte transformation. In addition, lymphocytes from individuals with low serum IgD levels exhibited a significant response to anti-sigma, whereas, those with normal or slightly elevated levels of serum IgD showed minimal stimulation. This study is the first to provide evidence that cell surface IgD may regulate metabolic functions of lymphocytes and is consistent with the idea that IgD is a 'triggering' receptor.