Complement Receptor 1 Expression Is Associated with Lower 24-Hour Proteinuria Level and Five-Year IgAN Progression Risk

Background: IgA nephropathy is the most common cause of glomerulonephritis diagnosed by kidney biopsy. Complement activation plays an important role in the pathogenesis of IgA nephropathy.CR1 (complement receptor 1, also known as CD35), is a negative complement activation regulator that was proven to be positive in podocytes in healthy patients. Methods: In this study, we recruited 86 patients who were diagnosed with IgA nephropathy by kidney biopsy in out center from March 2021 to August 2023. We conducted immunohistochemistry staining for CR1 and calculated the mean positive area for each glomerulus in every biopsy sample and clinical data were collected and analyzed. Results: Of the 86 patients, the median CR1 positive area in glomerulus of each patient was 8.0% and 58 patients had CR1 positive area ≥10%. The 24-hour proteinuria level [1.5 (1, 2.73) vs 0.89 (0.56, 1.38), p=0.0164] (g) and the 5-year IgA nephropathy progression risk [0.01683 (0.0806, 0.3773) vs 0.0775 (0.0539, 0.132), p=0.0014] was significantly higher in patients with CR1 positive area <10% than those ≥10%. The eGFR [71 (55, 98) vs 99 (75.5, 121.5)] (%) was significantly lower in patients with CR1 positive area <10% than those ≥10%. Conclusion: We conclude that decreased CR1 positive area in kidney biopsy samples is associated with higher 24-hour proteinuria level and 5-year IgA nephropathy progression risk. Funding: Government Support – Non-U.S.Table 1 Characteristics of patients with CR1 positive area <10% and those ≥ 10% with IgA Nephropathy.