Neutrophil phospholipase A2 activity in patients with SCD is shown. Purified neutrophils labeled with tritiated arachidonate were incubated with either rhGM-CSF or FCS for 20 minutes at 37°C, followed by stimulation for 15 minutes with either (A) PBS or (B) 1 μmol/L calcium ionophore, A23187. Phospholipase A2 activity was determined from the release of arachidonate into the supernatant as described in Materials and Methods, and expressed as the percentage of total cellular radioactivity. The data shown are the mean ±1 SE for 10 patients, compared with controls tested on the same day. The absolute values for the resting levels of arachidonate release shown in A are 3,204 ± 116 cpm/106neutrophils and 1,404 ± 211 cpm/106 neutrophils for SCD patients and their same-day controls, respectively. (B) Increments in arachidonate release above resting level after stimulation with calcium ionophore. Significant differences between patients and controls (Wilcoxon's matched pairs signed-ranks test) are shown: *P < .05, †P < .01. (▨), Patient; (□), control.
