CD40LG and systemic lupus erythematosus: Estimated Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score; total amount of protein in urine in 24 h; the serum levels of IgG, IgM, IgA, and C3; total B lymphocyte count (BLC); total white lymphocyte count (WBC); erythrocyte sedimentation rate (ESR); and C-reactive protein level were measured five times (at weeks 0, 4, 12, 24, and 52, respectively) in the two groups.<h4>Results</h4>Hypogammaglobulinemia was observed in 22/27 (81.5%) participants with LN prior to initiating treatment.