Impaired thymic output in patients with chronic hepatitis C virus infection.

Altered T cell homeostasis in chronic hepatitis C virus (HCV) infection has been demonstrated. However, it is unknown whether fibrosis is associated with more perturbed T cell homeostasis in chronic HCV infection. The aim of this study was to examine and compare T cell subsets including recent thymic emigrants (RTE), naive, memory, senescent, apoptotic and IL-7 receptor α (CD127) expressing CD4⁺ and CD8⁺ T cells as well as telomere length and interferon-γ production in HCV-infected patients with (n = 25) and without (n = 26) fibrosis as well as in healthy controls (n = 24). Decreased proportions of CD4⁺ and CD8⁺ RTE were found in HCV-infected patients, especially in HCV-infected patients with fibrosis (14.3% (9.7-23.0) and 28.8% (16.1-40.5), respectively) compared with healthy controls (24.2% (16.3-32.1), P = 0.004 and 39.1% (31.6-55.0), P = 0.010, respectively). Furthermore, HCV-infected patients with fibrosis presented with a higher proportion of CD4⁺ T cells expressing CD127 compared with HCV-infected patients without fibrosis [88.4% (84.5-91.0) versus 83.8% (79.9-86.8), P = 0.016]. Thus, impaired thymic output in HCV infection was found, and high proportion of CD127⁺ T cells may illustrate a compensatory mechanism to preserve T cell counts.