Specific binding sites for 1-O-alkyl-sn-glyceryl-3-phosphorylcholine on intact human blood neutrophils

Infection, inflammation and allergy are characterized by an infiltration of neutrophils or eosinophils in the tissue and are associated with an increased level of lysophospholipids. In this study it is shown that labeled 1-O-alkyl-sn-glyceryl-3-phosphorylcholine (lyso-paf) binds to intact human blood neutrophils. Unlabeled lyso-paf(500 nM) inhibits the binding of [3H]lyso-paf to neutrophils in the presence of fatty acid-free serum albumin (0.25%). A linear Scatchard plot analysis of the specific [3H]lyso-paf binding to neutrophils revealed a KD value of 9.2 nM with 4,100 lyso-paf binding sites per neutrophil at 4 degrees C. Lyso-paf increased the specific binding of labeled platelet-activating factor ([3H]paf) to neutrophils at 20 degrees C. The increased specific binding of labeled paf to neutrophils could only be demonstrated when sterile cell preparation methods were used. Intact human blood eosinophils did not express specific lyso-paf binding sites. These results suggest that the lyso-paf binding sites on neutrophils have an up-regulatory function for paf which might be involved in neutrophil-mediated disorders.