Defective CCR7 expression on dendritic cells contributes to the development of visceral leishmaniasis.

Interaction between dendritic cells (DCs) and T cells is essential for the generation of cell-mediated immunity. Here we show that DCs from mice with chronic Leishmania donovani infection fail to migrate from the marginal zone to the periarteriolar region of the spleen. Stromal cells were fewer, which was associated with loss of CCL21 and CCL19 expression. The residual stromal cells and endothelium produced sufficient CCL21 to direct the migration of DCs transferred from naïve mice. However, DCs from infected mice had impaired migration both in naïve recipients and in vitro, in response to CCL21 and CCL19. Defective localization was attributable to tumor necrosis factor-alpha-dependent, interleukin 10-mediated inhibition of CCR7 expression. Effective immunotherapy was achieved with CCR7-expressing DCs, without the need to identify protective Leishmania antigens. Thus defective DC migration plays a major role in the pathogenesis of this disease and the immunosuppression is mediated, at least in part, through the spatial segregation of DCs and T cells.