LPS/platelet-induced respiratory burst is also dependent on CD18 or PSGL-1. Purified and fixed platelets were mixed with PMNs, which were incubated with DCFH-DA, and respiratory burst was measured in a fluorescence reading device. Specific fluorescence index (SFI) of stimulated cells was obtained by subtraction of the background fluorescence of labeled cells incubated in medium alone. The enhancement of LPS-induced respiratory burst of neutrophils by platelets is neutralized by α-CD18 or in part by α–PSGL-1. Shown is the mean of doublets of at least 3 experiments plus or minus SD after 125 minutes. Asterisks indicate statistically significant differences calculated by Student t test (P < .01).