Since T regulatory cells (Tregs) characterized as CD4+CD25+FoxP3+ (forkhead box P3) cells have emerged pivotal in suppressing autoimmune diseases like type 1 diabetes and others, this review is focused on evaluating the role of Treg defects or dysfunctions in MS- and MG-related autoimmune pathology [1, 13–17]. This evidence concerns the gene FOXP3 and type 1 diabetes mellitus.