C4A and systemic lupus erythematosus: The C3 concentrations between SLE patients with LN and without LN were 0.51 ± 0.03 μg/mL and 0.69 ± 0.04 μg/mL, respectively (p = 0.0018) (Figure 3(a)); the C4 concentrations between SLE patients with LN and without LN were 0.086 ± 0.01 μg/mL and 0.115 ± 0.01 μg/mL, respectively (p = 0.0508) (Figure 3(b)).