Hepatitis C virus infection after liver transplantation is associated with lower levels of activated CD4 + CD25 + CD45RO + IL‐7rα high T cells

The expression of interleukin 7 receptor alpha high (IL‐7Rα high ) discriminates between activated CD25 + CD45RO + CD4 + T cells [IL‐7Rα high and forkhead box P3–negative (FoxP3 − )] and regulatory T cells (IL‐7Rα low and FoxP3 + ). The IL‐7Rα high CD25 + CD45RO + CD4 + FoxP3 − T cell population has been shown to be expanded in the blood and tissues of patients after kidney transplantation and to contain alloreactive T cells (activated T cells). In the present study, we analyzed the distribution of IL‐7Rα high CD25 + CD45RO + CD4 + FoxP3 − T cells in the blood of 53 patients after liver transplantation. The IL‐7Rα high CD25 + CD45RO + CD4 + FoxP3 − T cell population was significantly expanded ( P < 0.0001) in stable transplant recipients versus healthy donors. However, the magnitude of the expansion was significantly higher ( P < 0.0001) in liver transplant recipients with no hepatitis C virus (HCV) infection in comparison with those with a preexisting HCV infection. Interestingly, effective suppression of HCV viremia after antiviral therapy was associated with an increase in the IL‐7Rα high CD25 + CD45RO + CD4 + FoxP3 − T cell population to levels comparable to those of liver transplant recipients not infected with HCV. The present results indicate that (1) the IL‐7Rα high CD25 + CD45RO + CD4 + FoxP3 − T cell population is expanded after liver transplantation, (2) it is a valuable immunological marker for monitoring activated and potential alloreactive CD4 T cells in liver transplantation, and (3) a preexisting HCV infection negatively influences the expansion of this population in liver transplant recipients. Liver Transpl 16:49–55, 2010. © 2009 AASLD.