BLTR mediates leukotriene B4-induced chemotaxis and adhesion and plays a dominant role in eosinophil accumulation in a murine model of peritonitis

Leukotriene B-4 (LTB4) is a potent chemoattractant active on multiple leukocytes. including neutrophils, macrophages, and eosinophils, and is implicated in the pathogenesis of a variety of inflammatory processes. A seven transmembrane-spanning, G protein-coupled receptor, called BLTR (LTB4 receptor), has recently been identified as an LTB4 receptor. To determine if BLTR is the sole receptor mediating LTB4-induced leukocyte activation and to determine the role of LTB4 and BLTR in regulating leukocyte function in inflammation in vivo, we generated a BLTR-deficient mouse by targeted gene disruption. This mouse reveals that BLTR alone is responsible for LTB4-mediated leukocyte calcium flux, chemotaxis, and firm adhesion to endothelium in vivo. Furthermore, despite the apparent functional redundancy with other chemoattractant-receptor pairs in vitro, LTB4 and BLTR play an important role in the recruitment and/or retention of leukocytes, particularly eosinophils, to the inflamed peritoneum in vivo. These studies demonstrate that BLTR is the key receptor that mediates LTB4-induced leukocyte activation and establishes a model to decipher the functional roles of BLTR and LTB4 in vivo.