ICOS and type 1 diabetes mellitus: Other candidate genes are protein tyrosine phosphatase non-receptor type 2 (PTPN2), interleukin genes (such as IL4, IL13, IL4R, IL10), insulin receptor substrate 1 (IRS-1), inducible T cell costimulator (ICOS) and small ubiquitin-like modifier 4 (SUMO4), which modulate susceptibility to T1D or disease progression [12, 23].