Despite the expansion of circulating Tregs and the promising clinical results in early trials of hepatitis C virus-induced vasculitis [202], GvHD [200,208], T1D [12], SLE [209,210], and alopecia areata [211], low IL-2 monotherapy in double-blind, placebo-controlled trials was not sufficient to provide clinically relevant improvements [212,213], nor promote liver allograft tolerance [214]. Here, IL2 is linked to type 1 diabetes mellitus.