These parasites can also co-opt the host cells to produce PGD2 through direct cell damage provoked by their movement through the host tissue or the release of factors that signal innate immune cells such as mast cells, eosinophils, and macrophages or nonhematopoietic cells to produce PGD2 and modulate the parasite infection (Kubata, 2007) (Fig. 3b). The gene discussed is HPGDS; the disease is parasitic infectious disease.