Human antigen-specific IgA responses in blood and secondary lymphoid tissue: an analysis of help and suppression.

Antigen-specific IgA responses to influenza virus were obtained from lymphocytes derived from human secondary lymphoid tissue but not from the circulating pool (blood). T helper cells for IgA were present in both the circulating pool and secondary lymphoid tissue, were of the Leu-3A+ subset, and were relatively radioresistant. In addition, T alpha cells were shown to be important, but not crucial, for IgA helper responses. T cell-dependent suppression of IgA responses was demonstrated with T cells from both mucosal and systemic lymphoid tissue and was mediated by a radiosensitive Leu-2a+ cell. In contrast to T cells, functional B cell precursors for antigen-specific IgA responses were found only in secondary lymphoid tissue and not in the circulating pool.