Actions of PGD2and 15-deoxy-Δ12,14-PGJ2. PGD2 acts via the DP1 receptor, which acts via adenylyl cyclase, and chemoattractant receptor-homologous molecule expressed on T helper 2 cells (CRTH2). DP1 receptor is expressed in mast cells and eosinophils. CRTH2 is expressed on a small population of CD4 and CD8 T lymphocytes and in peripheral blood eosinophils and basophils. See text for details. AP-1, a family of transcription factors; PPARγ, peroxisome proliferator-activated receptor γ; IκK, IκB kinase; STAT-1, signal transducer and activator of transcription 1.