Abstract
Human peripheral blood leukocytes were isolated by sedimentation in the presence of 6% (w/v) dextran and neutrophils were purified on a Conray-Ficoll gradient. Also, human peripheral blood platelets were separated by a gel filtration method with Sepharose 2B. O-2 generation was measured by 2-methyl-6- [p-methoxyphenyl] -3, 7-dihydroimidazo [1, 2-a] pyrazin-3-one (MCLA) -dependent luminescence.
Addition of 0.5μM MCLA and 10-8 M fMLP or 10 ng/ml PMA to a suspension of platelets caused no significant MCLA-dependent luminescence. O-2 generation by neutrophils from healthy human volunteers, activated by 10-8 M fMLP or 10 ng/ml PMA, was inhibited by their platelets in a concentration-dependent manner.
On the other hand, platelets from a 30 year-old female severe bronchial asthmatic patient (atopic and perennial type), whose peripheral blood platelets were elevated more than 60×104/mm3, failed to cause an inhibition of O-2 generation from neutrophils activated by 10-8 M fMLP. The lack of an inhibition of the luminescence from neutrophils by platelets might be involved in the pathogenesis of bronchial asthma.
