Representative electric cell-substrate impedance sensing tracing. Change in normalized monolayer resistance with respect to time. t = 0 represents the time of addition of thrombin, media, untreated neutrophils from a healthy volunteer (normal), N-formyl-l-methionyl-l-leucyl-l-phenylalanine (fMLP)-treated neutrophils from the same healthy volunteer (normal/fMLP), untreated neutrophils from a septic patient (septic), or fMLP-treated neutrophils from the same septic patient (septic/fMLP). fMLP treatment was undertaken using 10–6 M fMLP. All neutrophil populations were found to cause a progressive loss of barrier function.