The Influence of Anti-C3aR and Anti-C5aR Antibody Levels on the Course of Specific Glomerulonephritis Types

Background: The complement system factors' role in the pathogenesis of autoimmunological diseases is known, but the influence of autoantibodies against complement factors' receptors on the course of specific glomerular diseases remains unclear. 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). These conditions were compared to a healthy control group (n = 22). Then, for up to two years, we tracked the patients' clinical progress (in terms of creatinine, total protein, and albumin levels) and compared the outcomes with their antibody levels. Results: The lupus nephritis group had higher levels of anti-C3aR and anti-C5aR antibodies than the other groups. The lupus nephritis group's anti-C3aR antibody level showed a negative correlation with albumin and total protein at several time points of observation. Additionally, at numerous observational points, the anti-C3aR antibody level showed a positive correlation with both the basic albumin level in the FSGS group and the total protein level. Conclusions: The anti-C3aR and anti-C5aR antibodies are higher in lupus nephritis patients compared to other glomerulonephritis patients and healthy individuals. Albumin and total protein levels appear to be correlated positively with anti-C3aR antibody levels in FSGS and negatively in lupus nephritis.