SLE patients with high disease activity showed significantly restricted microbiota diversity.RG relative abundance correlated with lupus disease activity. Anti-RG antibodies were directly correlated with SLEDAI scores and anti-DNA levels, but negatively correlated with C3 and C4. Patients with active lupus nephritis showed highest levels of serum anti-RG antibodies. This evidence concerns the gene C3 and systemic lupus erythematosus.