Inhibition by histamine of platelet-activating-factor-induced neutrophil chemotaxis in bronchial asthma.

Circulating human polymorphonuclear neutrophils are involved in asthma after their migration into the lung by local chemotactic factors. Investigation of the locomotion of neutrophils in Boyden chambers, showed that the chemotactic intensity of the platelet-activating factor (PAF) was similar in cells from healthy subjects and allergic asthmatics, although the optimal effect of the mediator was observed at 10(-6) M and 10(-8) M, respectively. Histamine had no direct chemoattractant effect on neutrophils but inhibited PAF-induced chemotaxis of neutrophils from healthy subjects and allergic asthmatics. This study provides additional evidence that neutrophils are involved in asthma, and points out the interaction between PAF and histamine in the migration of neutrophils to the lung.