We and others have established BLT1-knockout (BLT1KO) mice [7, 8], and previous studies using BLT1KO mice showed that LTB4-BLT1 signaling is involved in a variety of inflammatory and immune responses, including allergic airway inflammation [4, 7, 9, 10], multiple sclerosis [11], atherosclerosis [3, 12, 13], inflammatory arthritis [14, 15], tumor promotion [16], and psoriasis [17]. This evidence concerns the gene LTB4R and psoriasis.