In vitro maturation of monocyte-derived dendritic cells results in two populations of cells with different surface marker expression, independently of applied concentration of interleukin-4.

Dendritic cells (DCs) play a crucial role in the development of adaptive immune response. Monocyte-derived dendritic cells (MDDCs) are generated in vitro to study DC biology and for use in immunotherapy. However, procedures to generate MDDCs vary and an impact this may have on their final phenotype is insufficiently studied. Monocytes isolated from healthy blood donors were cultured for 7 days with granulocyte-macrophage colony stimulating factor (50 ng/mL) and low (500 IU/mL, L-IL4) or high (1000 IU/mL, H-IL4) interleukin 4 (IL4), to obtain immature DCs and for the following 2 days with addition of soluble CD40 ligand (500 ng/mL) and prostaglandin E ₂ (1 μg/mL) to obtain mature DCs. We measured mean fluorescence activity and percentage of cells, positive for CD14, HLA-DR, CD80, CD83, CD86, CCR7, and CD1a or CD209 markers after 7 and 9 days of culture, in both IL4 concentrations. Percentage of positively staining mature MDDCs was higher than among immature cells, for all studied markers. Interestingly, varying IL4 concentrations had negligible impact on staining of mature MDDCs. However, immature L-IL4 cultured MDDCs were less intensely stained for HLA-DR and CD209 than H-IL4 immature DCs. Flow cytometry revealed presence of 2 populations of cells (dominant P1 and less prevalent P2), when either L-IL4 or H-IL4 was used. Among mature MDDCs, population P1 had higher percentage of positively staining cells than P2, for all studied markers except CCR7. In conclusion, both concentrations of IL4 produce in vitro heterogeneous populations of mature MDDCs with similar staining for cell surface markers.
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