Monocyte-derived dendritic cell function in chronic hepatitis C is impaired at physiological numbers of dendritic cells.

Monocyte-derived dendritic cells (MoDCs) are a promising cellular adjuvant for effector immune responses against tumours and chronic viral infections, including hepatitis C virus (HCV). If autologous DC therapeutic approaches are to be applied in persistent HCV infections in patients, it is important to have an unambiguous understanding of the functional status of the cell type used, namely MoDCs from patients with chronic hepatitis C (CHC) infection. Because of conflicting published reports of either impaired or normal MoDC function in CHC infection, we re-examined the ability of MoDCs from CHC and normal healthy donors (NHD) to mature to an inflammatory stimulus [tumour necrosis factor (TNF)-alpha] and their subsequent functional capabilities. Expression of maturation-associated phenotypic markers [human leucocyte antigen (HLA)-DR, CD83, CD86, CD40], allostimulatory capacity in mixed lymphocyte reactions (MLRs) and CD40-ligand-induced cytokine and chemokine generation were compared in CHC- versus NHD-MoDCs. TNF-alpha-stimulated CHC-MoDCs up-regulated phenotypic markers, but to significantly lower levels than NHD-MoDCs. At physiological ratios of DCs to T cells, CHC-MoDCs were less allostimulatory than NHD-MoDCs, but not when DC numbers were substantially increased. CHC- and NHD-MoDCs generated equivalent amounts of cytokines [TNF-alpha, interleukin (IL)-1beta, IL-6, IL-12p70, IL-15, IL-10] and chemokines [interferon-inducible protein (IP)-10, macrophage inflammatory protein (MIP)-1alpha, regulated upon activation, normal T expressed and secreted (RANTES)] after CD40 ligation. Because the functional defect was not apparent at high MoDC : T cell ratios, autologous MoDC therapy with sufficiently high numbers of DCs could, in theory, overcome any impairment of MoDC function in CHC.