Inhibition of interleukin synthesis and T cell proliferation by a monoclonal anti-Ia antibody.

The proliferative response in vitro of Lewis rat spleen cells to Con A was inhibited by a monoclonal antibody, OX4, with specificity for a public rat la antigen. Inhibition was dose-dependent and was observed only if the antibody was present during the first 48 hr of culture. OX4 anti-la antibody inhibited production of IL 1 by peritoneal exudate cells activated by lipopolysaccharide and inhibited the production of IL 2 by spleen cells activated by Con A. Addition of exogenous IL 1 to spleen cell cultures inhibited by OX4 anti-la antibody augmented production of IL 2 and returned the proliferative response of T cells to levels observed in Con A-stimulated cultures. We suggest that OX4 anti-la antibody reacts with la+ accessory cells to inhibit production of IL 1, which in turn limits production of IL 2 and finally T cell proliferation.