On the role of I‐A antigens in lectin‐ and antigen‐induced interleukin 2 production

Abstract

The role of I‐A molecules in lectin‐ and antigen‐induced interleukin 2 (IL2) production has been analyzed using monoclonal antibodies. Both lectin‐ and antigen [plus major histocompatibility complex (MHC)]‐induced IL2 production were profoundly inhibited by monoclonal anti‐I‐A antibodies, whereas monoclonal anti‐D and anti‐K antibodies had no effect. The anti‐I‐A‐mediated inhibition of lectin‐induced IL2 production was fully overcome by addition of interleukin 1 (IL1), while no recon‐stitution was observed in antigen (plus MHC)‐specific induction. Anti‐I‐A antibodies were also found to inhibit the T cell‐independent induction of IL1 production. I‐A antigens appear, therefore, to play two distinct roles in the induction of IL2 production: (a) I‐A molecules are directly involved in mediating activation signals to the macrophages at the level of IL1 production; (b) I‐A epitopes act as restricting elements in specific antigen recognition by T helper cells at the level of IL2 production, a requirement which is overcome by lectin.