C3 and systemic lupus erythematosus: In addition, the correlation between the differences in the expression of lymphocyte subpopulations in various clinical subtypes of SLE and the clinical laboratory indexes, such as SLE disease activity index (SLEDAI) score, complement C3, complement C4, IgG, IgA, IgM, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), were analyzed.