Pal K, et al. - Whether the benefit of 5-lipoxygenase (5-LO) inhibition in patients with severe asthma could be mediated in part by inhibition of eosinophil-derived LTB4, was investigated. Researchers found that BAL fluid from patients with severe asthma, including those with isolated eosinophilic inflammation, exhibited elevated LTB4 levels. Via immunohistochemistry (IHC), LTA4 hydrolase (LTA4H) was shown by these eosinophils. Using flow cytometry, IHC, and qPCR, LTA4H expression by blood eosinophils was corroborated. In response to some, but not all, stimuli, they found that blood eosinophils robustly produced LTB4. Overall, LTA4H transcripts and protein were expressed by eosinophils. Also, eosinophils could be stimulated to secrete LTB4. An increased eosinophil-derived LTB4 was speculated in many asthmatics, which could contribute to the efficacy of 5-LO inhibition.