T2D subjects had an increased percentage of CD19+CD23+ (B-2) cells and a decreased percentage of CD19+CD23− (B-1) cells attributing to CD19+CD23−CD5− (B-1b) cells, but not CD19+CD23−CD5+ (B-1a) cells, compared to NGT and IGR subjects. This evidence concerns the gene FCER2 and type 2 diabetes mellitus.