H4 histamine receptor HRH4 SP9144 Pfi-013 GPCR105 IUPHARobj:265 protein H4R A histamine receptor that is a translation product of the human HRH4 gene or a 1:1 ortholog thereof. The preferred ligand is histamine. This receptor is expressed primarily in the bone marrow and eosinophils but also in a wide variety of peripheral tissues, including the heart, kidney, liver, lung, pancreas, skeletal muscle, prostate, small intestine, spleen, testis, colon, fetal liver and lymph node. G-protein coupled receptor 105 PR:000001565 AXOR35 GPRv53 HH4R Category=gene. histamine receptor