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CONTROL OF CLONED ALLOREACTIVE T LYMPHOCYTE PROLIFERATIVE RESPONSES: A POSSIBLE ROLE FOR CELL‐SURFACE-BOUND ALLOANTIGEN

Previous studies using flow cytofluorometry demonstrated that passively acquired alloantigens encoded by the I-A and H-2K/D regions of the MHC could be identified on the surface of murine cloned T lymphocytes. The present studies were designed to further characterize the nature of that bound alloantigenic material on cloned lines of alloreactive amplifier T cells (Th). Immune precipitation and polyacrylamide gel electrophoresis were used to substantiate that allogeneic I-A and H-2K/D antigens were present on the surface of these cloned Th. Using proteolytic digestion with papain, bound allogeneic I-A and H-2K/D was removed from the surface of a cloned Th designated L2. Allogeneic I-A or H-2K/D antigens were not reexpressed if papain digested cells were incubated overnight in culture medium without addition of fresh alloantigen. Further, cloned cells did not release detectable amounts of Interleukin 2 (IL-2) in response to Con A stimulation immediately following enzymatic digestion. After overnight culture, papain-digested cells released amounts of IL-2 similar to untreated controls. The proliferative response of these cells measured by 3H-Thymidine incorporation, however, was significantly less than that observed using undigested controls, unless alloantigen was provided in the form of fresh irradiated stimulating cells. The addition of partially purified preparations of monoclonal anti Ia antibodies to cultures of cloned Th resulted in marked reduction in incorporation of 3HTdR. These findings are consistent with the hypothesis that modulation of the Th proliferative response may occur at least partially through binding of allogeneic material to the cell surface.