Prevention of diabetes in the BB rat by early immunotherapy using Freund's adjuvant.

The BB rat spontaneously develops an insulin-dependent diabetes mellitus (IDDM) that closely resembles this disease in man. The pathogenesis involves autoimmune destruction of pancreatic islet beta-cells. In the present study, a single intraperitoneal injection of complete Freund's adjuvant (CFA) in diabetes-prone (DP) BB/Wor rats between 9 and 28 days of age reduced the incidence of diabetes at 120 days from 89% to 10-28%, whereas injection of CFA after 40 days of age was ineffective. The CFA-injected, diabetes-free DP rats had normal levels of pancreatic insulin and little or no mononuclear leukocyte infiltration in the islets. These protective effects of CFA were not associated with any changes in peripheral blood leukocyte counts or monoclonal antibody-defined T cell, B cell, or macrophage subsets in the spleen of the DP rats. These results suggest that it is possible to prevent diabetes by adjuvant treatment in early life without general immunosuppression or sustained therapy.