The successful allotransplantation of neonatal rat islets across multiple combined major and minor histocompatibility barriers

Cultured neonatal rat islets were transplanted across six strain combinations into nonimmunosuppressed allogeneic recipients. Islets were isolated nonenzymati-cally by an in vitro method and were cultured at 37°C in 5% CO₂ in air for 10 days prior to transplant. Transplants to nondiabetic recipients across four allogeneic barriers resulted in morphologically intact and well-granulated islet tissue present at the graft site in 54 of 55 cases for periods lasting as long as 445 days (mean day of sacrifice was 163). In trials using diabetic recipients, ACIs receiving WF islets (n = 3) and outbred Holtzmans receiving Holtzman islets (n = 3) were reversed and did not return to the hyperglycemic state for experimental periods of up to 430 days.