C3 and systemic lupus erythematosus: To assess whether ICPs proliferative activity clusters reflected a specific SLE phenotype, we evaluated clinical findings (SLEDAI, anti-DNA antibody titer, C3 and C4 levels, and Pt count), immunological factors (IL-6, IL-8, IL-10, the bioactivity of IFN-I, and TLR9 expression), and clinical symptoms (fever, arthritis, rash, and renal involvement) in each cluster.