GAD1 and diabetes mellitus: In conclusion, we have reported that T1D could be subtyped into four groups based on anti-GAD Ab and IgE profile, as follows: Subtype 1, the major classical Th1 cell-dependent autoimmune T1D; Subtype 2, the second major group associated with TYK2 promoter variant and maybe with virus-induced diabetes; Subtype 3, both Th1 and Th2 cells overactivated-immune condition; and Subtype 4, Th2 cell skewed-immune condition.