The objective of this proposal is to analyze the regulation of the immune response to cell bound antigen, when both antigen induced and idiotype induced regulatory events are initiated. These studies will focus on structure/function analysis of idiotype bearing antigen specific suppressor T cell (STC) derived molecules elicited by administering azobenzenearsonate (ABA) (a hapten known to elicit a cross-reactice idiotype (CRI) antibody response) coupled to syngeneic cells, intravenously (i.v.) to A/J mice. ABA specific STC derived suppressor factor(s) (SF) inhibit the development of ABA specific T cell function. Analysis of this SF material will be revealing in terms of: (1) the presence of idiotypic (Id) determinants encoded by VH genes and VK-1 genes on STC derived SF; 2) the role of H-2 MHC encoded elements, and subregion origin of structures on SF; 3) mechanisms by which STC and SF indice and initiate other regulatory events in vivo; and 4) the genetic restriction of Id positive STC or SF in terms of transferrable suppression. The analyses will be extended to use Id coupled cells, and anti-Id antiserum to analyze receptor initiated regulatory events relevant to the functioning antigen specific T cell level. These studies should result in knowledge useful in understanding the regulatory mechanisms initiated once antigen perturbs the immune system.