Effect of ovarian hormones on maturation of dendritic cells from peripheral blood monocytes in dogs

Previously, we reported that ovarian hormones affect the immune response againstE. coli isolated from the dogs affected with pyometra. In order toinvestigate mechanisms underlying the immune modulation, we examined the effects ofovarian hormones on the generation of dendritic cells (DCs), the most potent antigenpresenting cell. DCs were differentiated from peripheral blood monocytes (PBMOs) using acytokine cocktail. Both estrogen receptor and progesterone receptors were expressed by thePBMOs and immature DCs. When various ovarian hormones were added to the culture for the DCdifferentiation, progesterone significantly decreased the expression of DC maturationmarkers, such as CD1a, CD80 and CD86, on mature DCs. Conversely, the addition of estrogento the cultures increased the expression of CD86, but not other maturation makers.Furthermore, DCs differentiated in the presence of progesterone did not stimulateallogeneic mononuclear cells in PB. Taken together, these results indicate thatprogesterone diminishes the maturation of DCs, leading to decreased immune responsesagainst invading pathogens.