C3 and systemic lupus erythematosus: The expression of circ-Rac GTPase activating protein 1 (RACGAP1) was downregulated in SLE PBMCs and related to SLEDAI, anti-dsDNA, and C3 levels, which participated in SLE pathogenesis by regulating the PTEN/AKT signaling pathway through binding to miR-22-3p (121).