G protein-coupled receptor primarily expressed in immune cells such as mast cells, eosinophils, basophils, dendritic cells and neutrophils that plays a key role in immune and inflammatory responses (PubMed:26948974). Mediates chemotaxis of immune cells to sites of inflammation or injury by responding to histamine (PubMed:26948974). Activation by histamine also influences the release of proinflammatory cytokines such as TNF, CCL4, IL6 and IFN-gamma (PubMed:29600327, PubMed:31583075). Ligand binding induces a conformation change that triggers signaling via G(i)/GNAI1 leading to decreased intracellular cAMP levels by inhibiting adenylate cyclase activity (PubMed:39333117). In addition, plays a role in the control of renal reabsorption processes, particularly albumin uptake (By similarity). {ECO:0000250|UniProtKB:Q91ZY2, ECO:0000269|PubMed:12503632, ECO:0000269|PubMed:26948974, ECO:0000269|PubMed:29600327, ECO:0000269|PubMed:31583075, ECO:0000269|PubMed:39333117}. This is the function of ENSG00000134489 (HRH4, histamine receptor H4).