Pathogenic and Protective Roles of CD45RB^low CD4⁺ Cells Correlate With Cytokine Profiles in the Spontaneously Autoimmune Diabetic Mouse Free

The adoptive transfer of splenocytes from diabetic NOD mice to NOD-scid/scid (NOD-scid) recipients results in diabetes. This model was used to test the effect of cotransfer of splenocyte subsets from young nondiabetic NOD mice. As shown previously in other NOD models, the CD4⁺ subset from young nondiabetic mice significantly delayed the onset of diabetes in splenocyte cotransfers (P < 0.001). The data presented here showed that the development of diabetes in NOD-scid recipients correlated with a rapid increase in peripheral CD45RB^low CD4⁺ cells. However, the CD45RB^low subset of CD4⁺ cells from young nondiabetic mice protected from diabetes transfer in this model. We therefore examined whether CD45RB^low CD4⁺ cells from diabetic mice were pathogenic rather than protective. CD45RB^low CD4⁺ splenocytes from diabetic NOD mice were transferred along with CD8⁺ splenocytes from diabetic mice into NOD-scid recipients, and all of the recipients became diabetic within 5 weeks posttransfer. In contrast, no recipients (0 of 10) of CD45RB^high CD4⁺ cells along with CD8⁺ splenocytes from diabetic mice became diabetic within 5 weeks posttransfer (P < 0.001). A correlate for the difference between CD45RB^low CD4⁺ cells from diabetic NOD mice and CD45RB^low CD4⁺ cells from nondiabetic mice, which showed protective effect in splenocyte cotransfers, was found in cytokine production after stimulation with anti-CD3 antibodies in vitro. CD45RB^low CD4⁺ cells from diabetic mice showed a significantly higher ratio (approx-imately fivefold) of γ-interferon (IFN-γ) to interleukin (IL)-4 when compared with CD45RB^low CD4⁺ cells from nondiabetic mice (P < 0.001). In conclusion, the function of the CD45RB^low population of CD4⁺ cells changes from a protective to a pathogenic one during the development of disease in the NOD mouse. This change in function correlates with cytokine production in vitro; increased IFN-γ-to-IL-4 ratio is associated with pathogenic potential and occurs coincident with (or after) the onset of diabetes.