Expression of programmed death-ligand 1 on peripheral blood T cells and its correlation with liver inflammation grade in patients with type 1 autoimmune hepatitis

Objective To investigate the expression of programmed death-ligand 1 (PD-L1) on the surface of peripheral blood CD4+and CD8+T cells and its correlation with liver inflammation grade in patients with type 1 autoimmune hepatitis (AIH) . Methods A total of 62 patients with type 1 AIH (43 in the active stage and 19 in the remission stage) who were admitted to Mengchao Hepatobiliary Hospital of Fujian Medical University from January 2014 to August 2017 were enrolled, and 20 healthy persons were enrolled as control group. Flow cytometry was used to measure the expression of PD-L1 on the surface of eripheral blood CD4+and CD8+T cells. The t-test or the Mann-Whitney U test was used for the comparison of continuous data between two groups, and a one-way analysis of variance and the least significant difference t-test or the Kruskal-Wallis H test were used for the comparison between multiple groups; the chi-square test was used for comparison of categorical data between groups; Pearson correlation and Spearman rank analysis was performed to investigate correlation.Results Compared with the control group, the type 1 AIH group had significantly higher expression rates of PD-L1 on the surface of peripheral blood CD4+and CD8+T cells (10. 94% ± 4. 52%/9. 93% ± 3. 32% vs 5. 42% ± 2. 64%/4. 86% ± 2. 16%, t = 7. 12 and 6. 41, both P < 0. 05) ; compared with the remission stage group and the control group, the active stage group had significantly higher expression rates of PD-L1 on the surface of peripheral blood CD4+and CD8+T cells (12. 45% ± 5. 61%/11. 13% ± 4. 63% vs 7. 88% ± 3. 85%/7.36% ± 3. 12% and 5. 42% ± 2. 64%/4. 86% ± 2. 16%, F = 15. 76 and 13. 54, both P < 0. 05) , and the remission stage group also had significantly higher expression rates than the control group (both P < 0. 05) . There were gradual increases in the expression rates of PD-L1 on the surface of peripheral blood CD4+and CD8+T cells in the patients with type 1 AIH in G0 group (7. 88% ± 3. 85% and 5. 36% ±3. 12%) , G1-2 group (10. 13% ± 4. 74% and 10. 45% ± 4. 34%) , and G3-4 group (15. 63% ± 5. 98% and 14. 73% ± 5. 12%) (χ2=12. 14 and 10. 32, P < 0. 05) . In the patients in the active stage of type I AIH, the expression rates of PD-L1 on the surface of peripheral blood CD4+and CD8+T cells were positively correlated with total bilirubin, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transpeptidase, and immunoglobulin G (CD4+T cells: r = 0. 687, 0. 736, 0. 702, 0. 647, and 0. 824, all P < 0. 01; CD8+T cells: r = 0. 673, 0. 719, 0. 680, 0. 631, and 0. 817, all P < 0. 01) ; the expression rates of PD-L1 on the surface of peripheral blood CD4+and CD8+T cells were also positively correlated with liver inflammation grade (rs= 0. 768 and 0. 721, both P < 0. 05) . Conclusion In patients with type I AIH, high expression of PD-L1 on peripheral blood T cells is closely associated with liver inflammation grade, suggesting that PD-L1 may be involved in the development and progression of type 1 AIH.