PGE2 up-regulates C5aR on DC and prevents its down-regulation upon maturation. Immature DC were incubated with CD40L or LPS, respectively, with or without the presence of PGE2 for 48 hr. The expression of C5aR and CD83 was analysed by fluorescence cytometry. Presence of PGE2 led to up-regulation of C5aR, while LPS and CD40L led to down-regulation. (a) One representative experiment (numbers are percentage of cells in the corresponding quadrants), (b) mean fluorescence intensity ± SEM (of all cells acquired) of five independent experiments (*, significant difference, P < 0.05).