P4HB and type 1 diabetes mellitus: Importantly, they detected an autoreactive T-cell response in the sera from T1D patients to carbonylated prolyl-4-hydroxylase b subunit (P4Hb; also known as PDIA1), an enzyme required for the formation of proinsulin disulfide bonds (179), highlighting a potential role of PC in generating neo-antigens in T1D.