Administration of the protein hormone insulin can result in adverse immunological reactions that complicate the mangement of diabetes mellitus. Both IgE-mediated allergic reactions and IgG-mediated resistance are well-documented. In addition, insulin antibodies are present in most patients and may have subtle effects on diabetes control by altering pharmacokinetics and by accelerating vascular disease. These problems have not been eliminated by therapy with human insulin preparations. Insulin immunity is also part of the autoimmune prodrome of untreated Type I diabetes. This laboratory is examining the cellular and humoral mechanisms that regulate the immune response to insulin in man. In contrast to animal models, studies of human T cells show that the immunogenic determinants are often not predicted from amino acid differences. This complex human immune response includes T lymphocytes and antibodies that are specific for autologous insulin. In the proposed work, several approaches will be used to dissect this complex immune response. Insulin specific T cell clones have been produced, and these clones recognize distinct epitopes on the molecule in association with Class II MHC antigens. Using this approach, genetic elements that restrict T cell responses to the principal antigenic determinants on human and animal insulin will be identified. In addition, these clones will be used to investigate the role of antigen catabolism in the activation of T cells reactive to autologous, human insulin. To dissect the antibody response in these same subjects, monoclonal antibodies that recognize idiotopes on human anti-insulin antibodies were produced. These shared idiotopes are found on circulating anti-insulin antibodies and on antibodies produced by insulin-specific B cell lines from a number of subjects. These reagents will be used to initiate molecular studies of the germline and somatic mechanisms that generate the diverse anti-insulin repertoire in man. These studies are designed to identify the principal mechanisms that regulate insulin immunity in both treated patients and in Type I diabetics prior to insulin therapy. This information will provide insight into the role of insulin immunity in the pathogenesis of Type I diabetes and may identify therapeutic alternatives for the management of adverse immunological reactions.
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