BLT1 and BLT2: the leukotriene B4 receptors

Two receptors for leukotriene B₄ (LTB₄) have been molecularly identified: BLT1 and BLT2. Both receptors are G protein-coupled seven transmembrane domain receptors, whose genes are located in very close proximity to each other in the human and mouse genomes. The two receptors differ in their affinity and specificity for LTB₄: BLT1 is a high-affinity receptor specific for LTB₄, whereas BLT2 is a low-affinity receptor that also binds other eicosanoids. The two receptors also differ in their pattern of expression with BLT1 being expressed primarily in leukocytes, whereas BLT2 is expressed more ubiquitously. By mediating the activities of LTB₄, these receptors participate both in host immune responses and in the pathogenesis of inflammatory diseases. Reduced disease severity in animal inflammatory models seen with LTB₄ receptor antagonists and in mice with targeted deletion of BLT1 have revealed important roles for LTB₄ and its receptors in regulating pathologic inflammation.