A group of patients with small-vessel vasculitis, involving arterioles, capillaries, and venules, and glomerulonephritis have serum anti-neutrophil cytoplasmic antibodies (ANCA).56 ANCA are produced by T cells and activate leukocytes and monocytes, which result in damage to blood vessel walls, further attracting more leukocytes and prolonging the inflammatory process.57 ANCA antibodies are of two types, anti-proteinase-3 (PR3) or anti-myeloperoxidase (MPO). Here, MPO is linked to glomerulonephritis.