The mean titer of IL-21 by ELISA in serum samples from patients with AIH (294.3 pg/ml) was significantly higher than in those with DILI (72.8 pg/ml, p < 0.0001), PBC (74.1 pg/ml, p < 0.0001), acute hepatitis B (52.6 pg/ml, p < 0.0001), CHC (60.8 pg/ml, p < 0.0001), NASH (37.9 pg/ml, p < 0.0001), and viral hepatitis (78.6 pg/ml, p < 0.0001), and in sera from healthy volunteers (46.9 pg/ml, p < 0.0001) (Fig. 1). The gene discussed is IL21; the disease is hepatitis B virus infection.