Previous studies have shown that multiple transfusions of spleen cells from histocompatible nondiabetic donors prevent autoimmune diabetes mellitus in diabetes-prone (DP) BioBreeding/Worcester (BB/Wor) rats. In this study, a single transfusion of ≥50 × 106 cells from either diabetes-resistant (DR) BB/Wor or Wistar-Furth (WF) rats substantially reduced the incidence of diabetes when given to DP rats 27 or 46 days old but not 61 days old. Transfusion and protection were associated with the appearance of RT6+ donor lymph node cells in recipient rats. In vivo depletion of RT6+ T-lymphocytes in 150-day-old protected animals did not produce diabetes. DR BB/Wor and WF spleen cells were equally efficacious when given either intraperitoneally or intravenously. Mitogen-activated spleen cells were relatively less effective than untreated cells. We conclude that BB rat diabetes can be prevented by one transfusion of spleen cells from histocompatible DR and WF donors, and that the protective effect is dependent on recipient age and cell dose. The effect may be mediated by a population of RT6+ T-lymphocytes that, during a critical developmental period, regulate the expression of autoimmunity in these animals.

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