Histamine release from human leukocytes by platelet-activating factor

Platelet-activating factor (PAF) was found to induce histamine release from human basophils in mixed leukocytes in the presence of cytochalasin B. The reaction was rapid and dependent on temperature. The release was lower at a high concentration of PAF and was inhibited by EDTA, suggesting a noncytolytic mechanism. CV-3988, a PAF antagonist, inhibited the reaction dose-dependently. PAF acted as an IgE-independent stimulus, but PAF-induced histamine release from leukocytes of allergic asthmatics, who had elevated serum IgE levels, was significantly higher than that from leukocytes of controls. These results suggest that PAF-induced histamine release is useful for studying the role of PAF in the pathogenesis of allergic disorders including bronchial asthma.