Transforming growth factor beta decreases the immunogenicity of rat islet xenografts (rat to mouse) and prevents rejection in association with treatment of the recipient with a monoclonal antibody to interferon gamma.

Culture of rat islets of Langerhans for 1 week at 37 degrees C with recombinant transforming growth factor beta prolonged the survival of islet xenografts transplanted into diabetic mouse recipients. Treatment of diabetic recipients with a neutralizing monoclonal antibody to murine interferon gamma did not affect the survival of islet xenografts cultured 7 days in control medium. However, treatment of donor islets with transforming growth factor beta in combination with treatment of diabetic recipients with interferon gamma antibody produced a 75% survival of the islet xenografts at 100 days. Fifty percent of the recipients who had accepted their graft for more than 100 days were immune unresponsive to a transplant of freshly isolated islets from the same donor strain.