IGF1 and autoimmune disease: Here, we show that recombinant human insulin-like growth factor-1 (rhIGF-1) stimulates proliferation of both human and mouse regulatory T (Treg) cells in vitro and when delivered systemically via continuous minipump, it halts autoimmune disease progression in mouse models of type 1 diabetes (STZ and NOD) and multiple sclerosis (EAE) in vivo.