Abstract: Objective The purpose of this study was to investigate serum peripheral blood leukocyte differentiation antigen 38 (CD38) and interleukin 21 (IL-21) level changes and their implications in patients with autoimmune hepatitis (AIH). Methods 53 patients with AIH were admitted to our hospital between October 2018 and October 2021, and all underwent liver biopsies. The patients were clinically defined to mild or moderate and severe degree of the disease. Serum CD38 and IL-21 levels were determined by enzyme-linked immunosorbent assay. The univariate and multivariate Logistic regression analysis were applied to analyze the factors affecting the intrahepatic tissue inflammatory activity, and the area under the receiver operating characteristic curve (AUROC) was applied to judge the diagnostic efficacy. Results Serum bilirubin, ALT, AST, CD38, IL-21 levels, the incidence of liver cirrhosis and the percentage of intrahepatic lymphocyte infiltration in portal area in 19 patients with severe degree of AIH were(89.4±15.2)μmol/L,(179.3±36.5)U/L,(216.1±37.6)U/L, (19.0±4.5)pg/mL, (367.8±62.0)pg/mL, 36.8% and 84.2%, all significantly higher than [(36.5±6.8)μmol/L, (61.2±25.9)U/L, (78.7±33.8)U/L, (11.1±2.3)pg/mL, (209.5±46.2)pg/mL, 8.8% and 5.9%, respectively, P<0.05] in 34 patients with mild/moderate AIH; serum CD38 and IL-21 levels in 23 patients with G3-G4 AIH were (21.8±4.4)pg/mL and (387.1±59.7)pg/mL, both significantly higher than [(12.4±2.3)pg/mL and (194.6±45.5)pg/mL, respectively, P<0.05] in 30 patients with G1-G2; the multivariate Logistic regression analysis showed that serum bilirubin, CD38 and IL-21 levels and intrahepatic lymphocyte infiltration in portal area were all the independent risk factors for severe liver tissue injury (P<0.05); the ROC analysis showed that the AUC was 0.939, with the sensitivity of 82.6% and specificity of 96.7% when the combination of serum CD38 (20.4 pg/mL as the cut-off-value ) and IL-21 (379.3 pg/mL as the cut-off-value) was applied to predict the intrahepatic inflammatory activity, superior to any one of the two parameter. Conclusion Serum CD38 and IL-21 levels increase in patients with autoimmune hepatitis, as the disease deteriorate, and the clinicians might predict the disease severity based on this phenomenon.

Key words: Autoimmune hepatitis, Leukocyte differentiation antigen 38, Interleukin 21, Histological activity index