PBMCs from SLE patients (n=23) were cultured for 10 days in medium devoid of human serum, after which IgG was measured by ELISA in the culture supernatants. (A) Correlation between level of spontaneous IgG production and disease activity (SLEDAI score) was analyzed with the Spearman's rank correlation test (rs=0.6022, P=0.0024). (B) Comparison of spontaneous IgG production between patients with inactive disease (SLEDAI<6, n=16) and active disease (SLEDAI ≥6, n=7) using the Mann-Whitney test (**, P<0.01). Horizontal lines represent mean ± SD. (C) Comparison of spontaneous IgG levels between patients treated with no or low dose prednisone treatment (<10 mg/day, n=16) and higher dose treatment (≥10 mg/day, n=7) using the Mann-Whitney test. Each data point represents one individual sample. * indicates P<0.05.