This study aims to deepen understanding of lymphocyte phenotypes related to the course of hepatitis C virus (HCV) infection and progression of liver fibrosis, in a cohort of atomic-bomb survivors. The study subjects comprise three groups: 162 HCV persistently infected, 145 spontaneously cleared, and 3511 uninfected individuals. We found increased percentages of peripheral blood TH1 and total CD8 T cells and decreased percentages of NK cells in the HCV persistence group, compared with the other two groups, after adjustment for age, gender, and radiation exposure dose. Subsequently, we found that increased TH1 cell percentages in the HCV persistence group were significantly associated with an accelerated time-course reduction in platelet counts―accelerated progression of liver fibrosis―while TC1 and NK cell percentages were inversely associated with the progression. This study suggests that TH1 immunity is enhanced by persistent HCV infection, and that percentages of peripheral TH1, TC1, and NK cells may help predict progression of liver fibrosis.

This research was based on RERF Research Protocols 3-09, 4-02, 2-00, 9-92, and was supported in part by the U.S. National Institute of Allergy and Infectious Diseases (NIAID Contract HHSN272200900059C).