Prostaglandin D2 affects the maturation of human monocyte-derived dendritic cells:: Consequence on the polarization of naive Th cells

Among the factors produced at inflammatory sites and those capable of modulating dendritic cell (DC) functions, PGD, may be important in the outcome of immune responses. The biological roles for PGD, are in part effected through two plasma membrane G protein-coupled receptors: the D prostanoid (DP) receptor and the chemoattractant receptor-homologous molecule expressed on Th2 lymphocytes (CRTI12). In this report, we studied the effects of PGD, and of its major physiological metabolite, 15-deoxyDelta(12,14)-PGJ(2) (15d-PGJ(2)), on the functions of human monocyte-derived DC. First, we show that PGD(2) exerts in vitro chemotactic effects on monocytes via CRTH2 activation while it inhibits the chemokine-driven migration of monocyte-derived DC through DP. We also report that PGD2 and 15d-PGJ2 alter the LPS- and allergen-induced DC maturation and enhance the CD80/CD86 ratio on mature DC in a DP- and CRTH2-independent manner. Moreover, PGD2 and 15d-PGJ2 strongly reduce the secretion of the Th1 promoting cytokine IL-12 and affect the synthesis of chemokines involved in Th1 cell chemotaxis, particularly CXCL10. Inhibition of cytokine/chemokine secretion implicates at least in part DP, but not CRTH2. The effects exerted by PGD2 are associated with the phosphorylation of CREB, but do not parallel with the deactivation of the NF-kappaB and mitogen-activated protein kinase pathways. In contrast, 15d-PGJ2 seems to target other cellular proteins. Finally, in a model of Th CD45RA(+) differentiation induced by allergen- and superantigen-pulsed DC, PGD2 impacts on the orientation of the immune response by favoring a Th2 response.