This proposal is designed to study structural features of the antibody molecules that elicit auto-anti-idiotypic (AAI) immune responses in rabbits and to study the functioning of AAI T cells and T cell factors. Past work showed that unique reduction-sensitive idiotopes (RSID) regularly elicit natural AAI antibody responses in rabbits. The proposed research plan is designed to elicit immune responses in outbred rabbits, detect the appearance of immunoregulatory AAI antibodies by radioimmunoassay and to identify and purify the antibody clonotypes that elicited AAI responses by analytical and preparative isoelectric focusing. The purified RSID will be studied to determine which polypeptide chain bears the RSID. These chains will then be characterized for amino acid composition and amino acid sequences will be determined in order to locate the RSID in collaboration with Dr. Mike Kehoe at the Northeastern Ohio Universities College of Medicine. Functional studies of the interaction of idiotype and AAI will be done by studies of the spontaneous appearance and regulatory role of AAI T cells. These studies will be done using cryopreserved PBL taken during the response to determine if AAI T cells can affect immune reactivity of these cells. Isoelectric focusing technology will be used to purify circulating T cell receptors. These molecules will be purified and studied biochemically and serologically using monoclonal antibodies. Studies of internal image structures will be done by making monoclonal antibodies specific for rabbit b locus epitopes, making monoclonal anti-idiotype and characterizing the structural relatedness of the original epitope and the anti-idiotype. These projects exploit current biochemical and biophysical technology to gain insights into the mechanisms that are functioning in a normal immune response. The results will be relevant to understanding of pathogenesis of some autoimmune diseases, allergies, and transplantation rejection as will as characterizing new methodology for vaccine manipulation of the immune system.