Indeed, the negative association between PB Tgfb1 expression at 10-week and 14-week insulitis scores is consistent with previous reports demonstrating that islet protection by Foxp3+ regulatory T cells (Treg) is controlled by TGF-β.24 Consistent with this, a high frequency of intra-islet Treg has been demonstrated for up to 3 weeks after diabetes onset in NOD mice.25 Also consistent with our data, treatment of NOD mice with TNF during the insulitic phase suppressed diabetes development.26 This evidence concerns the gene TGFB1 and diabetes mellitus.