Although the frequency of proliferating CD62LloFoxP3+Tregs was also increased in the islets of NOD.B6Idd3 (55%) versus NOD (45%) mice, the difference between the two was not as great as that seen between the respective CD62LhiFoxP3+Tregs pools (Fig. 4A and B). This

finding suggests that CD62LhiFoxP3+Tregs are more sensitive to changes in the level of IL-2 than CD62LloFoxP3+Tregs. Elevated IL-2 expression by conventional T cells in NOD.B6Idd3 mice may therefore selectively increase proliferation (Fig. 4) and survival 24 of suppressor-efficient CD62LhiFoxP3+Tregs residing in the islets. IL-2 also has direct effects on CD62LloFoxP3+Tregs. As noted above, IL-2 converts a significant number of sorted CD62LloFoxP3+Tregs into CD62LhiFoxP3+Tregs in vitro (Fig. 6D), selleck compound possibly reflecting downregulation of the activation status of CD62LloFoxP3+Tregs. Indeed, IL-2 mediates both positive and negative effects on conventional T cells depending on the activational status of the cells 28, 47. selleck chemicals Finally, APC may also influence the CD62LhiFoxP3+Tregs to CD62LloFoxP3+Tregs

ratio in vivo. The type and activational status of professional APC can have a marked effect on FoxP3+Tregs induction/expansion. Groups have shown that macrophages and DCs exhibit an increased tolerogenic capacity in NOD.Idd3 versus NOD mice 48, 49; the mechanistic basis for this enhanced tolerogenic effect, however, has yet to be determined. Recent studies with NOD.Idd3 congenic

lines have shown that NOD-derived FoxP3+Tregs exhibit an impaired suppressor Pomalidomide purchase function 37, 38. Our results demonstrate that the limited suppressor activity reported for NOD FoxP3+Tregs is due to an increased number and frequency of suppressor-deficient CD62LloFoxP3+Tregs, which “dilute out” the suppressor-competent CD62LhiFoxP3+Tregs. The limited suppressor function of sorted NOD or NOD.B6Idd3 CD62LloFoxP3+Tregs was demonstrated in vitro (Fig. 5D), consistent with an earlier report 7. These results, however, differ from work published by Szanya et al., that demonstrated that CD62LhiCD4+CD25+ and CD62LloCD4+CD25+ T cells from the spleen of NOD mice differ in suppressor activity only in in vivo, but not in vitro, assays 19. The level of anti-CD62L Ab-binding and the gating scheme may account for differences in the frequency of and, in turn the in vitro suppressor activity of, the pool of CD62LloFoxP3+Tregs in the respective studies. In addition, Szanya et al. examined splenic-derived CD62LloFoxP3+Tregs, whereas in this study CD62LloFoxP3+Tregs were prepared from PaLN; “tissue residency” may also influence the suppressor activity of these T cells and contribute to the disparity between the studies. Reduced TGF-β1 7 expression relative to CD62LhiFoxP3+Tregs, however, is consistent with a diminished suppressor activity by CD62LloFoxP3+Tregs. In contrast to NOD mice, the increased frequency of CD62LhiFoxP3+Tregs in the PaLN and islets of NOD.