LYMPHOCYTE-T REQUIREMENT FOR DIABETES IN RT6-DEPLETED DIABETES-RESISTANT BB RATS

Diabetes-prone (DP) BB rats develop spontaneous autoimmune insulin-dependent diabetes mellitus (IDDM). The cell populations involved in the expression of diabetes are not precisely known but probably include natural killer (NK) cells, macrophages, and T lymphocytes. Because the DP rat has few lymphocytes of the CD5+/CD+ phenotype, cytotoxic T lymphocytes (T(c)) are not believed to be important in the process. Diabetes-resistant (DR) BB rats that are depleted of RT6+ T lymphocytes also become diabetic and provide an additional model of IDDM. We report that diabetes in DR rats depleted of RT6+ T lymphocytes is prevented by the concomitant depletion of either the CD5+ or the CD8+ population. In contrast, coadministration of anti-asialoganglioside(M1) (alpha-ASG(M1)), an antiserum that principally recognizes NK cells, failed to prevent hyperglycemia in RT6-depleted rats. We propose that the initiation of diabetes in both DP and RT6-depleted DR rats is T-lymphocyte dependent. However, the final common pathway leading to autoimmune beta-cell destruction in IDDM may be different in these models. The RT6-depleted DR rat requires a cell that is sensitive to anti-CD8 (possibly a T(c)), whereas the DP rat requires an anti-ASG(M1)-sensitive cell.