Although >97% of both patient and control CD4+ cells expressed the Treg signature molecule FOXP3, the CD4+CD25+FOXP3+ population, was significantly lower in APS-1 patients compared to healthy donors (mean patients 45.6%, mean controls 64.3%, p = 0.0009, Figure 4A). This evidence concerns the gene FOXP3 and autoimmune polyendocrine syndrome type 1.