N-formyl- l -methionyl- l -leucyl- l -phenylalanine treatment of primary sepsis leads to more profound loss of barrier function. Change in monolayer resistance at 30 minutes, 60 minutes, and 180 minutes. Groups were analyzed using two-way repeated-measures analysis of variance with Holm–Sidak post-hoc analysis. Values presented as mean ± standard error of the mean. Whereas primary sepsis (PS) neutrophils could be further stimulated at every time point (a), this effect was only present at 30 minutes for secondary sepsis (SS) neutrophils; no difference was noted thereafter (b). *P <0.05. fMLP, N-formyl-l-methionyl-l-leucyl-l-phenylalanine.