Itami H, Hara S, Samejima K, et al. - Given that the revised Oxford classification of IgA nephropathy (IgAN) explains that there is a link between cellular/fibrocellular crescents and poor renal prognosis, proposing an extension to the MEST-C score, and given that a pivotal role of complement activation in IgAN pathogenesis has been reported, therefore, researchers performed this study with 132 IgAN patients diagnosed by renal biopsies. Participants were divided into C ≥ 1 and C0 groups. Comparisons of clinical, light microscopic, and immunofluorescent characteristics were performed. Experts found lower average age and rate of hypertension, and higher score of urinary occult blood and E score in the C ≥ 1 group. Average immunofluorescence scores for IgA, C5b-9, mannose-associated serine protease (MASP) 1/3, MASP2, properdin, factor B, and kappa were identified to be significantly higher in the C ≥ 1 group. Findings showed a correlation between crescent formation in IgAN and activation of the lectin and alternative pathways. Significantly increased use of steroids was observed in the C ≥ 1 group, which was suggested to be the likely reason for comparable renal function during the follow-up period.