RELEASE OF PLATELET-ACTIVATING-FACTOR FROM STIMULATED ASTHMATIC EOSINOPHILS

We examined platelet-activating factor (PAF)-like activity in eosinoph ils obtained from asthmatic and nonasthmatic patients. PAF-like activi ty was detected by aggregation of washed guinea Pig platelets. Eosinop hils from asthmatic patients stimulated with C5a (a human complement f actor), N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP), or calci um ionophore A23187 had a mean activity of 8.86 +/- 1.99 ng/10(6) cell s in the supernatants and 20.34 +/- 7.11 ng/10(6) cells in the cell pe llets, 10.75 +/- 0.78 and 25.44 +/- 5.23, and 12.89 +/- 1.74 and 36.67 +/- 6.43, respectively. Mean PAF-like activities in eosinophils from nonasthmatic patients stimulated with Cia, fMLP, or A23187 were 5.91 /- 0.23 ng/10(6) cells in the supernatants and 9.12 +/- 1.95 ng/10(6) cells in the cell pellets, 6.99 +/- 0.93 and 7.09 +/- 1.11, and 7.22 /- 1.42 and 9.78 +/- 2.03, respectively. With no stimulation, mean PAF -like activities in both eosinophil populations were under the detecti on limit in the supernatants and in the cell pellets. PAF-like activit y was greater in asthmatic eosinophils than in nonasthmatic eosinophil s after stimulation with C5a, fMLP, or A23187, suggesting that asthmat ic eosinophils contribute to the development of bronchial asthma by in ducing more PAF-like activity.