C4A and type 1 diabetes mellitus: C4 is a gene of the highly variable complement pathway situated ∼500 kb from DRB1 and DQB1 and strongly associated with diverse AIDs (Hauptmann et al., 1974; Hou et al., 2013; Cleynen et al., 2016), so some scientists also carried out numerous researches to uncover whether C4 is associated with T1DM development.