This study showed that the correlation between sFas and IL-18 in LN (P < 0.001, rp = 0.5) is significantly stronger than it is in mild SLE (P < 0.001, rp = 0.4) with similar nonrenal SLEDAI score (P = 0.032, z = 1.85). The gene discussed is IL18; the disease is systemic lupus erythematosus.