Addition of ketamine reduces the percentage of CD1a-positive cells in interleukin-4 granulocyte–monocyte colony-stimulating factor (IL-4&GM-CSF)-cultured monocytes (MOs) after 5 days of incubation, suggesting diminished rate of differentiation of monocytes into immature dendritic cells (A and B). (A) Shows the aggregated data from all experiments (n = 133). (B) Shows the data in which all four experimental groups were set up at the same time (n = 14). Concomitantly, ability of IL-4&GM-CSF-differentiated MO to uptake (C) and process (D) antigen is severely affected if ketamine was present during their differentiation process, confirming that ketamine prevents acquisition of typical feature for dendritic cells by IL-4&GM-CSF-stimulated MO (green line = IL-4&GM-CSF alone; red line = IL-4&GM-CSF + ketamine; gray histogram = negative control). 4&G = interleukin-4 and granulocyte macrophage colony-stimulating factor stimulated; 4&G+Ket100 = interleukin-4 and granulocyte macrophage colony-stimulating factor + ketamine 100 µg/ml stimulated; 4&G+Ket10 = interleukin-4 and granulocyte macrophage colony-stimulating factor + ketamine 10 µg/ml stimulated; 4&G+Ket1 = interleukin-4 and granulocyte macrophage colony-stimulating factor + ketamine 1 µg/ml stimulated.