As a well-known FPR antagonist, formyl peptide receptor antagonist Boc-Phe-Leu-Phe-Leu-Phe is used extensively in FPR research. In regard to neutrophils, it was found that treatment of mice with Boc-PLPLP results in 40% reduction in neutrophil counts recovered in bronchoalveolar lavage fluid, compared with infected mice receiving placebo.