GM-CSF Grown Bone Marrow Derived Cells Are Composed of Phenotypically Different Dendritic Cells and Macrophages

Granulocyte-macrophage colony stimulating factor (GM-CSF) has a role in inducing emergency hematopoiesis upon exposure to inflammatory stimuli. Although GM-CSF generated murine bone marrow derived cells have been widely used as macrophages or dendritic cells in research, the exact characteristics of each cell population have not yet been defined. Here we discriminated GM-CSF grown bone marrow derived macrophages (GM-BMMs) from dendritic cells (GM-BMDCs) in several criteria. After C57BL/6J mice bone marrow cell culture for 7 days with GM-CSF supplementation, two main populations were observed in the attached cells based on MHCII and F4/80 marker expressions. GM-BMMs had MHCII(low)F4/80(high) as well as CD11c(+)CD11b(high)CD80(-)CD64(+)MerTK(+) phenotypes. In contrast, GM-BMDCs had MHCII(high)F4/80(low) and CD11c(high)CD8 alpha(-)CD11b(+)CD80(+)CD64(-)MerTK(low) phenotypes. Interestingly, the GM-BMM population increased but GM-BMDCs decreased in a GM-CSF dose-dependent manner. Functionally, GM-BMMs showed extremely high phagocytic abilities and produced higher IL-10 upon LPS stimulation. GM-BMDCs, however, could not phagocytose as well, but were efficient at producing TNF alpha, IL-1 beta, IL-12p70 and IL-6 as well as inducing T cell proliferation. Finally, whole transcriptome analysis revealed that GM-BMMs and GM-BMDCs are overlap with in vivo resident macrophages and dendritic cells, respectively. Taken together, our study shows the heterogeneicity of GM-CSF derived cell populations, and specifically characterizes GM-CSF derived macrophages compared to dendritic cells.