In vivo-mobilized kidney dendritic cells are functionally immature, subvert alloreactive T-cell responses, and prolong organ allograft survival

Background. Migratory antigen-presenting cells resident in kidneys may have tolerogenic potential. Difficulties inherent in their isolation have limited their characterization. The authors examined the phenotype and function of murine kidney dendritic cells (DC) mobilized in vivo by systemic administration of fins-like tyrosine 3 kinase ligand (Flt3L). Methods. Monoclonal antibody staining was used to characterize DC subsets in situ, immediately after their isolation, and after lipopolysaccharide stimulation. Cytokine and CC chemokine receptor (CCR) gene expression was analyzed by RNase protection assay. Mixed leukocyte reactions were performed to assess DC allostimulatory ability and also the function of putative T-regulatory cells. In vivo DC trafficking was monitored by fluorescence imaging of dye-labeled cells and the influence of renal DC on vascularized heart allograft survival was determined. Results. Flt3L induced a marked increase both in CD11c(+)CD8alpha(-) and in CD11c(+)CD8alpha(+) DC within the renal cortex and medulla. Rarer, CD11c(+)B220(+) (precursor plasmacytoid) DC were also detected. Bulk freshly isolated DC exhibited no interleukin (IL)12p35 mRNA, low surface co-stimulatory molecule expression, and CCR transcripts, consistent with immaturity. They elicited only weak allogeneic T-cell proliferative responses, and repeated stimulation induced CD4(+)CD25(+) IL-10(+) T cells. In vivo, the freshly isolated DC failed to prime T cells of naive allogeneic hosts for anti-donor cytotoxic T-cell responses. When infused systemically, 1 week before organ transplantation, they prolonged graft survival without immunosuppressive therapy. Conclusions. Hematopoietin-mobilized renal DC are functionally immature and exhibit tolerogenic potential. Mobilization of DC within kidneys is likely to affect their antigen-handling capacity, immunogenicity, and tolerogenic ability.