LTB4R and rheumatoid arthritis: Studies using KO mice of LTA4 hydrolase and LTC4 synthase demonstrated that neutrophil-produced LTB4, but not CysLTs, contributed to joint bone erosion in the rheumatoid arthritis mouse model [24], while the LTB4 receptor BLT1 was involved in osteoclast activity during OVX-induced bone loss [18].