1), similar to other NOD mouse lines congenic for a resistant Idd3 locus 37–39. Consistent with previous findings 38 naïve CD4+ T cells

isolated from the spleen of NOD.B6Idd3 mice exhibited increased IL-2 secretion upon in vitro stimulation relative to NOD CD4+ T cells (Supporting Information Fig. 1). To determine the influence of Idd3 on FoxP3+Tregs, the frequency and number of gated CD4+CD3+ T cells expressing FoxP3 and CD25 (Fig. 2A) were assessed in the thymus, spleen, PaLN, and islets of age-matched NOD and NOD.B6Idd3 female mice via FACS. No difference in the frequency of FoxP3+Tregs was detected in the thymus of NOD and NOD.B6Idd3 mice suggesting that thymic development of FoxP3+Tregs is unaffected by IL-2 expression Olaparib levels. On the other hand, an increased frequency and number of FoxP3+Tregs was detected in the PaLN and spleen of older NOD.B6Idd3 mice relative to age-matched NOD mice (Fig. 2A–C). In addition, the frequency of FoxP3+Tregs was significantly increased in the islets of Apitolisib concentration 10- and 16-wk-old NOD.B6Idd3 versus NOD female mice (Fig. 2B). Notably, however, a greater number of FoxP3+Tregs were detected in the islets of older NOD mice (Fig. 2C) reflecting increased T-cell infiltration of the islets relative to age-matched NOD.B6Idd3

mice. These data demonstrate that the frequency of FoxP3+Tregs is increased in the PaLN and islets of NOD.B6Idd3 mice compared with NOD mice. We and others have shown that for CD62Lhi- versus CD62Llo-expressing FoxP3+Tregs exhibit increased suppressor activity 7, 19. Accordingly, CD62Lhi- and CD62Llo-expressing FoxP3+Tregs were examined

temporally in age-matched NOD.B6Idd3 and NOD female mice. Interestingly, age-dependent differences in the frequency and number of CD62Lhi- and CD62Llo-expressing FoxP3+Tregs were detected in the PaLN and islets of the respective groups of mice. NOD female mice exhibited a temporal decrease in the frequency of CD62LhiFoxP3+Tregs and a concomitant increase in CD62LloFoxP3+Tregs in PaLN (Fig. 3B). Although the number of CD62LhiFoxP3+Tregs progressively increased in the PaLN of NOD female mice (5.2×104 (4 wk) versus 9.0×104 (16 wk)), a greater increase in CD62LloFoxP3+Tregs numbers was detected (6.3×104 (4 wk) versus 14.9×104 (16 wk)) (Fig. 3C). In the PaLN of NOD.B6Idd3 mice, however, the frequency and number of CD62LhiFoxP3+Tregs showed no marked change with age, which were increased relative to age-matched NOD females (Fig. 3B and C). A similar scenario was observed in the islets of NOD and NOD.B6Idd3 female mice. A temporal increase in the frequency of CD62LloFoxP3+Tregs was detected in the islets of NOD female mice which was due to elevated numbers relative to CD62LhiFoxP3+Tregs (Fig. 3D and E). Despite a progressive decline, the frequency of CD62LhiFoxP3+Tregs in the islets of NOD.B6Idd3 female mice was elevated relative to age-matched NOD female mice (Fig. 3D and E).