Induction of tolerance-inducing antigen-presenting cells in bone marrow cultures in vitro using monoclonal antibodies to CD200R.

CD200 to CD200R interactions produce immunoregulation. We investigated whether the expression of CD200R on dendritic cell (DC) precursors affects their developmental fate. C57BL/6 bone marrow (BM) cells were cultured in vitro in the presence of (interleukin-4 + granulocyte-macrophage colony-stimulating activity) to generate allostimulatory DCs, which were in turn used to induce cytotoxic T-lymphocyte and cytokine production after culture with C3H responder spleen cells. Some marrow cultures included anti-CD200R antibodies. The inclusion of monoclonal antibodies in different isoforms of CD200R in the BM culture led to a generation of cells (tolerogenic DCs) that were unable to produce allostimulation in vitro with responder cells. Cells taken from these latter mixed leukocyte cultures (MLCs) now contained CD4(+)CD25(+) cells able to inhibit the antigen-specific MLC response of fresh C3H responder cells to stimulation with C57BL/6 cells, but not stimulation with BALB/c cells. Tolerogenic DCs, infused in vivo into mice receiving C57BL/6 skin grafts, produced antigen-specific decreased rejection of BL/6 allografts, not BALB/c allografts, compared with mice receiving control DCs (generated from BM in the absence of anti-CD200R). The induction of CD4(+)CD25(+) suppressor cells in MLCs using tolerogenic DCs from the initial BM cultures could be overcome by using limiting numbers of tolerogenic DCs and an excess of allostimulatory DCs derived from BM cultures maintained in the absence of anti-CD200R. These data indicate that anti-CD200R biases stem cells in BM toward the development of suppressive antigen-presenting cells, which can induce CD4(+)CD25(+) regulatory T cells. Tolerogenic DCs have the potential to modify graft acceptance in vivo.