The Differential Role of GM-CSF and Flt3L on Myelopoiesis of Lineage Negative Bone Marrow Cells

Abstract

Abstract During the inflammatory response, multiple cytokines drive myelopoiesis to expand innate cells. Of those cytokines, granulocyte-macrophage colony-stimulating factor (GM-CSF) and FMS-like tyrosine kinase 3 ligand (Flt3L) are known cytokines secreted during the immune response and drive myeloid and dendritic cell (DC) development. Though GM-CSF and Flt3L have been used for bone marrow differentiation culture, their specific role in myeloid and DC differentiation derived from lineage negative hematopoietic cells has not been studied. To compare the kinetics of myeloid and DC development under GM-CSF and Flt3L culture, we sorted and cultured lineage negative bone marrow (Lin− BM) cells from B6 mice in vitro using GM-CSF- or Flt3L-containing media. We found that Flt3L had the potential to produce both cDC1 (XCR1+) and cDC2 (CD11b+) DCs from the Lin− BM cells, whereas GM-CSF lacked the potential to produce XCR1+ cells. Flt3L culture preferentially differentiated Lin− BM cells into immature (MHCIIlo CD11cint) and mature (MHCII+ CD11chi) DCs, and monocytic Ly6C+ myeloid cells. However, GM-CSF culture condition influenced differentiation towards immature and mature cDC2s, and Ly6C+ monocytes and Ly6Ghi granulocytes. Flt3L and GM-CSF conditions were found to preferentially differentiate not only dendritic cell subsets but also myeloids. This study demonstrates the different roles of GM-CSF and Flt3L on myeloid and DC differentiation during in vitro Lin− BM culture.