title: The effects of phorbol ester on alloantigen presentation.
abstract: B cells and Ia+ thyroid cells fail to stimulate alloreactive T cells in a primary mixed leukocyte reaction (MLR) and fail to activate some allo-class II (I-A) reactive T cell hybridomas. We now demonstrate that B cells can specifically stimulate a primary MLR in combination with the phorbol ester, PMA, but not with interleukin 1 (IL 1) or calcium ionophore. The primary MLR induced with B cells plus PMA can be blocked by either monoclonal anti-I-A or anti-L3T4 antibodies. In contrast, thyroid cells that can be induced to express Ia antigens after incubation with interferon-gamma fail to stimulate a primary MLR even in the presence of PMA or IL 1. We confirmed these observations by using the alloreactive T cell hybridoma, HTB-9.3, which does not react to stimulator B cells. In the presence of PMA, however, this I-Ab-specific hybridoma line was able to respond to relevant but not to control stimulator B cells. Furthermore, the response of HTB-9.3 to B cells plus PMA was also blocked by anti-I-A or anti-L3T4 antibody. In contrast to B cells, Ia+ thyroid cells could not activate HTB-9.3 even in the presence of PMA or IL 1. The data indicate that for primary class II restricted allo-responses, B cells provide signals that can be complemented with the phorbol ester PMA, whereas Ia+ thyroid cells do not, suggesting the existence of additional requirements for T cell activation.
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D000001:Calcimycin / Q000494:pharmacology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D051379:Mice; D013601:T-Lymphocytes / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013961:Thyroid Gland / Q000276:immunology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D000949:Histocompatibility Antigens Class II; D000001:Calcimycin; D013755:Tetradecanoylphorbol Acetate