Prostaglandin D$2($PGD$2)$ was found to stimulate the migration of$,$ and cytokine production by$,$ ILC$2$s isolated from human skin. Thus, within four hours of stimulation, ILC$2$s began secreting IL$-4,$ IL$-5,$ and IL$-13$ in response to PGD$2.$ While most studies have documented a role for IL$-25,$ IL$-33,$ and TSLP derived from epithelial cells in activating cytokine production by ILC$2$s$,$ what do these data on PGD$2$ indicate?

ILC$2$s are unlikely to be important in allergic responses in the skin.Mast cells secreting lipid mediators can also activate ILC$2$s in the skin.

Lipid mediators, such as PGD$2,$ are the only mediators of inflammation during allergic responses in the skin.PGD$2$ is an important protease in degrading potential allergens that penetrate the skin.