Monocyte-derived DCs generated in the presence of FCS are CD1a⁺, exhibit a phenotype of intermediate maturity, and show a strong tendency to mature. (A) Cell surface marker expression by fluorescent flow cytometry analysis. Monocyte-derived DCs generated in the presence of FCS were more than 90% CD1a⁺HLA-DR^high, expressed intermediate levels of CD80 and CD86 and low levels of maturation marker CD83, and lacked CD25 expression. Furthermore, all DCs expressed CD11c and lacked monocytic marker CD14 (data not shown). Data are representative of 6 independent experiments. (B) Four-hour pulsing of DCs with KLH increases the number of CD83⁺ DCs. CD83⁺ cells were assessed after 7 days of culture plus or minus an additional 4-hour culture with KLH or complete medium (CM) as control. Indicated P value was obtained by an impaired t test. Significance was defined as P < .05. Symbols represent independent experiments.