Methods: We measured the levels of anti-C3aR and anti-C5aR antibodies in patients with membranous nephropathy (n = 18), primary focal and segmental glomerulosclerosis (FSGS) (n = 25), lupus nephritis (LN) (n = 17), IgA nephropathy (n = 14), mesangial proliferative (non-IgA) glomerulonephritis (n = 6), c-ANCA (cytoplasmic anti-neutrophil cytoplasmic antibodies) vasculitis (n = 40), and p (perinuclear)-ANCA vasculitis (n = 16). Here, C5AR1 is linked to focal segmental glomerulosclerosis.