PSB-16671 acts in an off-target, non-GPR84 mediated fashion in mouse bone marrow derived but not human neutrophils. Neutrophils were generated from mouse femur bone marrow taken from wild type (a) or GPR84 deficient (c) animals. PCR analysis shows genotyping from 4 wild type and 4 GPR84 knock-out mice (b). Membranes prepared from these cells were used in [35S]GTPγS binding studies to measure effects of varying concentrations of either 2-HTP or PSB-16671 (a(i), c(ii)). The ability of compound 107 (10 µM) to block the effects of 2-HTP (1 μM), PSB-16671 (10 μM) or DIM (30 μM) were also assessed (a(ii), c(i)). Neutrophil membranes prepared from human whole blood were used in [35S]GTPγS binding studies to assess the ability of compound 107 to block the effects of 2-HTP or PSB-16671 (d). Data represents means ± S.E.M. of combined data from experiments performed on membrane preparations from 3 individual donors. *p < 0.05, **p < 0.01, ***p < 0.001 relative to agonist only (two-tail t-test).