In vivo prevention of thyroid and pancreatic autoimmunity in the BB rat by antibody to class II major histocompatibility complex gene products.

Evidence is accumulating that the development of insulin-dependent diabetes mellitus involves autoimmune phenomena, both in the human and in the BB rat model. A strong association is observed in both cases with alleles of the class II major histocompatibility complex (MHC). Results of the present study show that autoimmune phenomena, as assessed by the presence of clinical diabetes or histological thyroiditis, are prevented by the injection of monoclonal antibodies to class II gene products in the BB rat. Immunosuppression was specifically obtained with a monoclonal antibody to the murine I-E equivalent, as opposed to the murine I-A equivalent, of the rat major histocompatibility complex. This represents indirect evidence for I-E subregion control of immune responses to islet cell and thyroid antigens in the BB rat model. The frequent occurrence of anaphylactic type deaths in young (1 month old) animals receiving more than six weekly injections of partially purified homologous (rat) monoclonal antibodies to rat class II gene products underscores the potential risks of this type of immunotherapy. The presumed immunologic mechanism (IgE antibody) and its specificity (anti-allotype, anti-idiotype, or anti-impurity) must be clarified to assess the risks and feasibility of this type of therapy.