Mammalian and viral IL-10 enhance C-C chemokine receptor 5 but down-regulate C-C chemokine receptor 7 expression by myeloid dendritic cells: impact on chemotactic responses and in vivo homing ability.

The immunosuppressive and anti-inflammatory cytokine IL-10 inhibits the phenotypic and functional maturation of dendritic cells (DC) and has been reported to confer tolerogenic properties on these important professional APC. Here, we exposed murine bone marrow-derived myeloid DC to either mouse (m) or viral (v) IL-10 early during their in vitro generation in response to GM-CSF and IL-4. Both mIL-10 and vIL-10 down-regulated the expression of CCR7 mRNA determined by RT-PCR, while mIL-10 up-regulated the expression of CCR5 transcripts. These changes in CCR7 and CCR5 expression were associated with inhibition and augmentation, respectively, of DC chemotaxis toward their respective agonists, macrophage inflammatory proteins 3beta and 1alpha, while in vivo homing of DC from peripheral s.c. sites to secondary lymphoid tissue of syngeneic or allogeneic recipients was significantly impaired. Anti-mIL-10R mAb reversed the effects of mIL-10 on CCR expression and restored DC homing ability. Retroviral transduction of mIL-10- and vIL-10-treated DC to overexpress transgenic CCR7 partially restored the cells' lymphoid tissue homing ability in allogeneic recipients. However, CCR7 gene transfer did not reinstate the capacity of IL-10-treated DC to prime host naive T cells for ex vivo proliferative responses or Th1 cytokine (IFN-gamma) production in response to rechallenge with (donor) alloantigen. These findings suggest that in addition to their capacity to subvert DC maturation/function and confer tolerogenic potential on these cells, mIL-10 and vIL-10 regulate DC migratory responses via modulation of CCR expression.