Autologous B lymphoblastoid cell lines and long-term cultured T cells as stimulators in the mixed lymphocyte reaction: analysis of the role of HLA class II antigens as stimulatory molecules.
Human activated T cells, long-term cultured in the presence of interleukin 2 (IL 2), were compared with autologous Epstein Barr virus-transformed B lymphoblastoid cell lines for expression of human leukocyte (HLA)-HLA-DR and -DQ antigens and for ability to induce proliferative responses in autologous and allogeneic lymphocytes. Immunofluorescence analysis performed with a panel of monoclonal antibodies (mAb) specific for HLA-DR or -DQ antigens did not reveal any significant difference in the expression of HLA-DR antigens but revealed reduced expression of HLA-DQ antigens on two out of four T cell lines tested. No obvious difference could be detected in the two-dimensional gel electrophoretic profile of HLA-DR and -DQ beta-chains synthesized by the autologous pairs of B and T cell lines. In contrast with previous reports, the IL 2-dependent cell lines consistently induced alloproliferative responses in standard 6-day mixed lymphocyte cultures; however, these responses were severalfold lower than those elicited by the autologous B lymphoid lines. Both anti-HLA-DR and anti-HLA-DQ mAb blocked the proliferative responses induced by the B cell lines but did not affect those generated by the T cell lines, suggesting that the latter cells induce T lymphocyte activation via a mechanism independent of HLA-DR or -DQ antigen expression on their surface. Addition of IL 2 to the mixed cultures with B cell lines as stimulators did not affect the outcome of the proliferative responses but partially or completely reversed the blocking activity of the mAb. In contrast, IL 2 significantly enhanced the alloproliferation induced by the T lymphoblastoid cell lines, and the anti-HLA class II mAb partially antagonized this effect. Taken together, these data suggest that unlike the HLA-DR and -DQ gene products on B cells, those on IL 2-dependent long-term cultured T cells do not play a direct or primary stimulatory role in the mixed lymphocyte reaction; the reduced levels of alloproliferation induced by the T cell lines are, at least in part, due to a defective production of endogenous IL 2 by the responder lymphocytes rather than to a defective expression of IL 2 receptors by the alloproliferative T cell subset; and the anti-HLA class II mAb in these cultures act only at the responder cell level, since they can efficiently block the enhancement of T cell proliferation triggered by exogenous IL 2, but not the proliferative responses induced by T cell lines in standard conditions.
D000911:Antibodies, Monoclonal / Q000502:physiology; D000954:Antigens, Surface / Q000032:analysis; D001402:B-Lymphocytes / Q000276:immunology*; D001667:Binding, Competitive; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D000949:Histocompatibility Antigens Class II / Q000032:analysis / Q000276:immunology*; D006801:Humans; D007376:Interleukin-2 / Q000502:physiology; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D000949:Histocompatibility Antigens Class II; D007376:Interleukin-2