Study Of PD-1 On CD8~+T Cells In Primary Biliary Cholangitis

Objectives This study aims to explore PD-1 on CD8+T cells in the pathogenesis of primary biliary cholangitis.Methods The CD8+T cells, PD-1+ cells and PD-1 expression on CD8+T cells in peripheral blood were analyzed by flow cytometry between PBC patients and healthy controls. Also, the mRNA of PD-1 in peripheral CD8+T cells was measured by RT-PCR. In addition, PD-1 expression on CD8+T cells was observed in liver biopsies between early and advanced stage PBC, using double immunofluorescence technology. The correlation between PD-1 expression on CD8+T cells and serum liver functional index was also analysed.Results The peripheral CD8+T cells (PBC 16.50%±5.16%, HC 22.22%±7.04%, P<0.05) and PD-1 expression (PBC 18.24%±4.98%, HC 23.32%±6.30%, P<0.05)on CD8+T cells of PBC patients were both lower than the control group, while there was no significant difference in peripheral PD-1+ cells (P=0.365).The results of RT-PCR indicated that the mRNA level of PD-1 in CD8+T cell was of no significant difference in two groups (P=0.123). In the liver biopsies of the early stage PBC patients, PD-1+ cells was significantly increased in the portal area than the advanced group, using the technology of immunofluorescence (early stage 5.506±0.901, advanced stage PBC 1.353±0.433, P<0.05). However, the difference of CD8+T cells and PD-1 expression on CD8+T cells were not significant between the two groups. Positive correlations between PD-1 expression on CD8+T cells in liver and serum TB, DB (r=0.491, P<0.05)、DB(r=0.564, P<0.05) were found.Conclusions PD-1 is involved in the pathogenesis of PBC, as its expression on peripheral CD8+T cells was decreased in PBC patients, compared to the health controls, suggesting that the immunosuppressive function of PD-1 on CD8+T cells was alleviated in PBC. In early stage PBC, the PD-1 expression was increased in portal tract areas than advanced stage patients, which maybe explained by the relatively more severe inflammatory reaction in early stage. The PD-1 expression on CD8+T cells in liver was of no significant difference between early and advanced stage, suggesting that the immunosuppressive function of PD-1 maybe similar.