MPO and rheumatoid arthritis: For example, immunoglobulin (Ig) G heavy chain/HLA-DR complexes in patients with rheumatoid arthritis (RA), myeloperoxidase/HLA-DR complexes in patients with microscopic polyangiitis, and thyroid-stimulating hormone receptor/HLA-DP complexes in patients with Graves’ disease were major targets for autoantibodies [2,3,4].