Background and Aims Chronic inflammation associated with hepatitis C virus (HCV) infection may lead to cirrhosis liver failure,or hepatocarcinoma;however,the pathogenic mechanism(s) involved in HCV immunopathology has not been completely understood.The current study explored the phenotypic and functional characteristics of γδ T cells and investigated their impact on liver pathology in chronically HCV-infected patients.Methods Blood samples were obtained from 51 patients with chronic HCV infection and 39 healthy volunteers (controls).The numeric,phenotypic and functional characteristics ofγδ T cells,subtype Vδ1 γδ T or Vδ2 γδ T were analyzed and we also investigated whether these immunological parameters were associated with clinical parameters (plasma viremia,ALT levels).Results We found that the proportion ofγδ T cells in blood samples from HCV-infected patients (7.77%) was much higher than in samples from healthy controls (4.01%;P < 0.05).This increase was due to expansion of subtype Vδ2 γδ T cells (6.57% vs 3.43%;P < 0.05),whilst Vδ1 γδ T cells were unchanged (0.898% vs 0.968%;P =0.4046).The percentage and absolute number of Vδ2 γδ T cells were positively correlated with serum ALT levels (r =0A049;P < 0.01 andr =0.3998;P< 0.01),but not with serum HCV RNA (r =0.0236;P =0.8822 andr =0.1646;P=0.2915).No correlation was found between the percentage and number of Vδ1 γδ T with either semmALTlevels or HCV RNA.Vδ2 γδ T cells from HCV-infected patients displayed an activated phenotype,which was indicated by increased expression of activation markers such as CD38,HLA-DR and CD69.Further analysis showed that Vδ2 γδ T cells from HCV-infected patients exhibited higher capacity to kill HepG2 targets in comparison with those from healthy subjects.Conclusion In HCV-infected patients,Vδ2 γδ T cells are activated and demonstrated enhanced eytolytic activity and might participate in liver injury during chronic HCV infection.These findings provide novel information regarding the pathogenesis of HCV infection.