Induction of immunoglobulin secreting cells in the human autologous mixed leukocyte reaction: regulation by helper and suppressor lymphocyte subsets defined with monoclonal antibodies.

The generation of IgM- and IgG-secreting cells in the human autologous MLR has been confirmed by using a microwell culture system and a reverse hemolytic plaque assay. The regulation of this response by T cell subsets was examined by using monoclonal antibodies that have previously allowed the definition of a Leu-3 helper/inducer subpopulation and a Leu-2 suppressor/cytotoxic subpopulation. These subsets were isolated by "panning" with monoclonal antibodies and were then cultured with autologous non-T cells, which serve as both stimulators of the reaction and a B cell source. The induction of antibody-forming cells was found to be dependent upon the Leu-3 subset whereas the Leu-2 subset not only failed to support C cell maturation, it actively suppressed the Leu-3 induced response. The Leu-3 response was found to be partially sensitive to radiation doses of 1000 rad or greater, whereas Leu-2 mediated suppression, even at high doses of cells, was totally ablated by 1500 rad. Thus, the generation of antibody-forming cells in the human autologous MLR is regulated by a balance of Leu-3 cell help and Leu-2 cell suppression. Such a finding may prove to be of relevance to immunoregulation in both health and disease.