The IL-21 levels in five AIH patients with elevated serum IgG4 (n = 5) were significantly higher than those in 17 AIH patients with normal IgG4 (F = 4.826, P < 0.05) and 29 sex- and age-matched healthy controls selected during the same visit period (F = 9.916, P < 0.01), with no significant difference between the latter two groups (F = 1.976, P=0.167) (Figure 3). The gene discussed is IL21; the disease is autoimmune hepatitis.