Pgd(2)/Crth2 Signaling Promotes Acquired Immunity Against Bee Venom By Enhancing Ige Production

IgE-dependent/independent activation of mast cell (MC) has been assumed to play a host defensive role against venom injection in skin. However, its detailed mechanisms remain unknown. We aimed to investigate the contribution of MC-derived prostaglandin D-2 (PGD(2))-mediated signaling in host defense against bee venom (BV). To achieve this, we utilized gene-deficient mice of a PGD(2) receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2). We first confirmed that subcutaneous injection of BV produced PGD(2) equally in wild-type (WT) and CRTH2-deficient (Crth2(-/-)) mice skins. The BV injection dropped body temperature and impaired kidney equally in both lines of mice. In WT mice, pre-injection of BV (3 weeks) significantly inhibited the hypothermia and kidney impairment caused by second BV injection. In contrast, this pre-injection was not effective for the second BV injection in Crth2(-/-) mice. We also found that BV injections increased serum BV-specific IgE levels in WT mice, and its serum transfused mice improved the BV-induced hypothermia in naive WT mice. In contrast, serum BV-specific IgE level was significantly lower in Crth2(-/-) mice. FACS analysis showed the BV injection stimulate migration of dendritic cells (DCs) into regional lymph nodes in WT mice. In Crth2(-/-) mice, its number was significantly smaller than that of WT mice. In conclusion, PGD(2)/CRTH2 signaling plays defensive role against second BV injection. This signaling promotes BV-specific IgE production at least partially by promoting DCs migration into regional lymph node.