2B). Since by using other combinations of inbred mouse strains we previously identified a locus quantitatively controlling thymic Treg-cell development on chromosome 17 [14], we assessed if the same locus was involved in the quantitative regulation of Treg-cell

differentiation in NOD mice. To address this question, we first analyzed the proportion of thymic CD25high CD4SP Treg cells in the congenic mouse strains NOD.B10-H2b and NOD.B6-H2b. These two congenic lines, that carry the B10- or B6-derived H2 locus of H-2b haplotype on an NOD genetic background, respectively, showed a ‘low’ (B6-like) percentage of Treg cells (data not shown). This observation indicated a major influence of an H2-linked locus on buy Lumacaftor the quantitative development of Treg cells. To better define the region of interest, we analyzed other recombinant NOD.B6 congenic

mouse strains [17]. NOD.B6-R76 (R76) mice carry a <20 Mbp B6-derived chromosomal region centromeric to the H2 locus. These mice displayed low (B6-like) proportions of thymic Foxp3+ CD4SP Treg cells. In contrast, thymocytes from the NOD.B6-R156 (R156) strain, carrying a distinct Decitabine order B6-derived region centromeric to H2, had high (NOD-like) proportions and numbers of Foxp3+ CD4SP Treg cells (Fig. 3A and B). Peripheral percentages and numbers of Treg cells were comparable in all the strains analyzed (Supporting Information Fig. 1). In conclusion, a ≤20 Mbp long region centromeric to the H2 complex on mouse chromosome 17 harbors a gene (or multiple genes) that quantitatively controls Treg-cell development. Interestingly, the Trd1 locus contains the diabetes susceptibility locus Idd16. The locus on chromosome 17 controlling Treg-cell development previously reported by us was located telomeric of

H2 and is therefore clearly distinct from the one we report here [14]. It was previously shown that R76 congenic mice develop diabetes with delayed kinetics when compared with those of NOD animals [17]. PAK6 To analyze whether changes in Treg-cell development may somehow be linked to diabetes by influencing Treg-cell function in the periphery, we compared NOD and R76 Treg-cell suppressive activity in vitro. We purified NOD and R76 CD4+CD25high CD127− splenic Treg cells and analyzed their capacity to inhibit proliferation of CD4+CD25−CD127+ splenic Tconv cells induced with plate-bound anti-CD3ε antibody. As shown in Supporting Information Fig. 2, NOD and R76 Treg cells inhibited proliferation of NOD and R76 Tconv cells with similar efficiency. Together, these data show that the intrinsic suppressive function of Treg cells and the sensitivity of Tconv cells to Treg-cell–mediated suppression are similar in NOD and R76 mice.