Monocytic myeloid-derived suppressor cells generated from rhesus macaque bone marrow enrich for regulatory T cells

Putative monocytic myeloid-derived suppressor cells (mMDSC; lineage(-)HLA-DR-/lo) were generated in 7-day cultures from normal rhesus macaque bone marrow (BM) cells in GM-CSF and IL-6. Three subsets were identified based on their differential expression of CD14, CD33, CD34 and CD11b. Following flow sorting, assessment of the capacity of these subsets to suppress anti-CD3/CD28-stimulated CD4 and CD8 T cell proliferation revealed that the most potent population was CD14(hi)CD33(-/lo)CD34(lo)CD11b(hi). These BM-derived mMDSC markedly increased the incidence of CD4(+)CD25(+)CD127(-)Foxp3(+) regulatory T cells in responder T cell populations. They offer potential value in testing the therapeutic efficacy of immunoregulatory mMDSC for the promotion of tolerance in nonhuman primate transplant models.