Hepatic and blood dendritic cell subsets in patients with chronic hepatitis C virus infection

Dendritic cells (DCs) are key mediators of innate anti-viral immunity being important detectors of viral infection and potent producers of Type I interferons (IFNs), IFN-αand IFN-β, as well as Type III IFNs, the IFN- λs. Successful adaptive anti-viral immunity also relies on the antigen presenting capacity of DCs and their production of cytokines that influence T cell polarisation. Defective immunity in patients with chronic Hepatitis C virus (HCV) infection has been proposed to be due to DC dysfunction which may also explain the poor success in generating therapeutic or preventative vaccination strategies for HCV infection. However, the many studies which have examined DC frequency and function in HCV patients to date have yielded conflicting results and the topic remains controversial. This may be because there are heterogeneous DC populations including myeloid and plasmacytoid lineages with various subsets of DCs having functional specialisations and different tissue localisation. In addition, little is known about the DC subtypes that predominate in human liver, the primary site of HCV replication, with the major studies being carried out in mice due to difficulty in obtaining human liver tissue and isolating DCs. Here we review the literature on DC subsets from HCV-infected blood and liver and make suggestions for future studies in this area that might lead to an improved understanding of HCV immunity and provide us with additional therapeutic targets.