Plaque-forming cell responses to trinitrophenyl (TNP)-L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT) in microcultures are not under conventional Ir gene control.

The IgM plaque-forming cell response to trinitrophenyl (TNP)-conjugated L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT) was studied in an in vitro microculture system. Contrary to expectations, this response was not found to be under conventional H-2 linked Ir gene control. Thus, both classical responder BALB/c (H-2d) and non-responder DBA/1 (H-2q) spleen cells gave equivalent anti-TNP PFC responses to TNP-GAT in these cultures. Experiments were performed to determined if haptenation had changed the GAT carrier so as to remove it from GAT-specific Ir gene control. It could be demonstrated that TNP-GAT elicited in vivo anti-GAT PFC responses showing typical Ir control in the BALB/c and DBA/1 strains; that anti-hapten and anti-carrier PFC responses to DNP-GAT in vivo were similarly controlled; and that the TNP-GAT compound remained a T cell- and Ia+ accessory cell-dependent antigen in vitro. Furthermore, the microculture system allowed GAT-specific T helper cells to be detected in the spleens of DBA/1 mice treated with GAT in vivo under conditions eliciting a predominant suppressor T cell response under usual conditions of assay. These findings contrast with the Ir gene regulation of TNP-(T,G)-A--L responses seen under identical culture conditions. The implications of these results for our understanding of the site of Ir gene action and the target of suppression in the GAT model are discussed.