C3 and systemic lupus erythematosus: CNS: central nervous system; ANA: antinuclear antibodies; dsDNA: double-stranded DNA; AnuA: anti-nucleosome antibodies; WBC: white blood cells; Hb: blood hemoglobin; PLT: blood platelets; ESR, erythrocyte sedimentation rat; CRP: serum levels of C-reactive protein; PCT: procalcitonin; Ig: immunoglobulin, C3: complement 3; C4: complement 4; SLEDAI: systemic lupus erythematosus disease activity index.