Histamine H4 receptor (H4R)

The histamine H4 receptor (H4R) is a member of the G protein-coupled receptor (GPCR) superfamily. It plays a central role in immunomodulation, regulating migration/recruitment of mast cells and eosinophils, modulating dendritic cell activation and T cell differentiation, and mediating chemotaxis for various immune cell types. Activation leads to the release of inflammatory mediators and amplification of chronic inflammatory responses. Selective antagonists are under investigation for allergy, asthma, pruritus and cancer.

H4R antagonists reduce symptoms/severity in asthma models where traditional antihistamines fail. Selective antagonists also reduce chronic itch/pruritus associated with atopic dermatitis.