Serum levels of anti-nuclear IgG4 in SLE patients were positively correlated with serum levels of C3 and albumin (r = 0.55, P < 0.05; r = 0.42, P < 0.05) (Figures 2(a) and 2(b)), negatively associated with 24-hour urinary protein (r = 0.47, P < 0.05) (Figure 2(c)), and positively correlated with serum levels of total IgG4 (r = 0.52, P < 0.05) (Figure 2(d)). This evidence concerns the gene C3 and systemic lupus erythematosus.