Expression of surface antigens during the differentiation of human dendritic cells vs macrophages from blood monocytes in vitro.

High expression of MHC antigens and adhesion/costimulation molecules is considered as one of the major characteristics qualifying macrophages (M) and dendritic cells (DC) as professional antigen presenting cells. Since accessory activity of M is known to be weaker than that of DC but both M or DC can differentiate from blood monocytes (MO) depending on culture conditions (i.e. GM-CSF vs GM-CSF/IL-4), we investigated the kinetics of expression of MHC antigens and several adhesion/costimulation molecules during the differentiation of DC or M from blood MO. Blood MO cultured with GM-CSF consistently induced M that showed adherence to plastic and CD14 expression. In contrast, MO cultured with GM-CSF/IL-4 rapidly became nonadherent, acquired DC morphology and lost CD14 expression. M but not DC proliferated as demonstrated by [H3]thymidine incorporation. MHC Class I was highly expressed in both M and DC. In contrast, MHC Class II molecules were significantly higher on DC compared to M. CD80 was upregulated on both DC and M but only on a subset of cells. CD80 expression peaked at day 3 on M and declined thereafter, while on DC expression increased significantly until day 10. CD86 was upregulated on the majority of DC and M. However, while M maintained stable expression of CD86 after day 3, DC progressively upregulated CD86 throughout the culture period. CD1a expression was initially low in both cell types and peaked at day 3 in M declining thereafter, while expression remained stable on DC until day 10. ICAM-1 expression was significantly upregulated on M when compared to DC at day 3. However, on M, ICAM-1 expression became undetectable by day 5 while on DC it increased through day 10. Similarly, CD40 was transiently expressed on M until day 5, while on DC it continuously increased until day 10. Finally, in contrast to other antigens, LFA-3 was always more strongly expressed on M than DC at all culture periods. Taken together, these data suggest that M showed a rapid but transient upregulation in the expression of adhesion/costimulation molecules, suggesting that maximal accessory ability is reached by M at an earlier time point than DC. Significant differences in surface antigen expression DC vs M were recognizable for MHC class II, CD86, CD80, CD1a, CD40 and ICAM-1. Specifically, major differences occurred for MHC class II, CD86, CD40 and ICAM-1. Therefore, the higher accessory ability of DC compared to M in naive T cell priming may be related to qualitative and quantitative differences in expression of these immunologically important surface molecules.