CD4 and chronic hepatitis C virus infection: In summary, the increased expression of inhibiting receptors, the lack of function of CD4+ cells, and the increased activity of Tregs all contribute to the impaired function of CD8+ lymphocytes in chronic hepatitis C (Boettler et al. 2005; Cabrera et al. 2004; Rushbrook et al. 2005; Semmo et al. 2005).