MPO and anti-neutrophil cytoplasmic antibody-associated vasculitis: The first study found that both major histocompatibility-complex (MHC) and non-MHC are associated with ANCA-associated vasculitis and also that anti-PR-3 ANCA is associated with HLA-DP and the genes encoding α1 antitrypsin and PR-3, while anti-MPO ANCA is associated with HLA-DQ [202].