GPR84 is a G protein-coupled receptor for medium-chain fatty acids. GPR84 is a receptor for free fatty acids and can be potently activated by saturated medium-chain free fatty acids (MCFAs) like decanoic acid, undecanoic acid and lauric acid. GPR84, a receptor for medium-length free fatty acids is upregulated on protein level in LPS activated tolerant CD14⁺ monocytes and THP-1 cells.

GPR84 is activated by MCFAs with the hydroxyl group at the 2- or 3-position more effectively than nonhydroxylated MCFAs. GPR84 is now considered to be a member of FFA-sensing GPCRs. MCFAs with carbon chain lengths of 9–14 activate GPR84, coupling primarily to a pertussis toxin (PTX)-sensitive G_i/o pathway. GPR84 should be a proinflammatory receptor and may be a novel, attractive target for treating chronic low grade inflammation associated-diseases.