GAD1 and systemic lupus erythematosus: Furthermore, the association of cTph cell frequency with clinical indexes such as SLE disease activity index (SLEDAI) or anti-double-stranded DNA antibodies in SLE (9–11), worsening renal function in IgA nephropathy (20), insulin autoantibodies (IAA), islet tyrosine phosphatase 2 antibodies (IA-2A), and glutamic acid decarboxylase (GAD) autoantibodies in type I diabetes mellitus (16) has also been reported.