The serum C3a levels in the AIH group were significantly higher than those in the control group at all AIH severities (HC, 1.60 μg/ml; mild AIH, 8.83 μg/ml; moderate AIH, 9.19 μg/ml; severe AIH, 8.32 μg/ml) (Fig. 1A). Here, C3 is linked to autoimmune hepatitis.