Heterogeneity of porcine bone marrow-derived dendritic cells induced by GM-CSF

In vitro generation of dendritic cells (DCs) is advantageous for overcoming the low frequency of primary DCs and the difficulty of applying isolation techniques for studying DC immunobiology. The culture of bone marrow cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) has been used extensively to generate bone marrow-derived dendritic cells (BMDCs). Studies have reported the heterogeneity of cells grown in murine GM-CSF culture based on the levels of MHCII expression. Although porcine DCs are generated by this classical method, the exact characteristics of the BMDC population have not yet been defined. In this study, we discriminated GM-CSF-grown BMDCs from gnotobiotic miniature pigs according to several criteria including morphology, phenotype, gene expression pattern and function. We showed that porcine BMDCs were heterogeneous cells that differentially expressed MHCII. MHCII(high) cells displayed more representative of DC-like morphology and phenotype, including costimulatory molecules, as well as they showed a superior T cell priming capacity as compared to MHCII(low) cell. Our data showed that the difference in MHCII(high) and MHCII(low) cell populations involved distinct maturation states rather than the presence of different cell types. Overall, characterization of porcine BMDC cultures provides important information about this widely used cellular model.