Autoimmune insulitis. Pathological findings in experimental animal models and juvenile diabetes mellitus

Organ-specific, species non-specific anti-pancreatic cellular immunity has been reported as a feature associated with juvenile diabetes of short duration. In order to further elucidate a possible causal relation between autoimmunity and juvenile diabetes morphological studies were made on an autopsy material from 12 juvenile onset diabetics, dying within 1 year after the onset of the disease. Each patient was compared with 2 age and sex matched controls. In the group of patients the islets of Langerhans showed the following characteristics: 1. The B cells were degranulated and present in reduced number, 2. The A cells appeared normal, 3. A lymphocytic, non-cicatricial insulitis was detected in 50% of the patients. Those findings were correlated with animal experiments, in which rats and mice were immunized with A: heterologous and homologous preparations of endocrine pancreas, in complete Freunds' adjuvant, B: heterologous and homologous insulin in complete Freunds' adjuvant, and C: complete Freunds' adjuvant. Only animals of group A developed spleen cell migration tests positive to the pancreatic preparations, lymphocytic infiltrations of the islets and degranulation of the B cells. In addition, the B cells showed ultrastructural signs of degeneration. The morphological changes were reversible and were accompanied by a transient reduction in glucose tolerance.