Platelet-activating factor in anaphylaxis and phagocytosis. I. Release from human peripheral polymorphonuclears and monocytes during the stimulation by ionophore A23187 and phagocytosis but not from degranulating basophils.

Platelet-activating factor (PAF) is a mediator of a anaphylaxis found initially in basophils and later in mouse and rat macrophages. The purpose of this paper was to determine the cellular origin of PAF released from human leucocytes and to establish if phagocytosis is a more important stimulus for PAF release than anaphylactic reactions. Phagocytic leucocytes (monocytes and PMNs) released PAF, physicochemically analogous to the PAF obtained by anaphylactic reactions in rabbits when challenged with zymosan, zymosan coated with complement, immune complexes, immunoglobulin aggregates or calcium ionophore A23187. Basophils failed to release PAF by anti-human IgE antibody, although positive degranulation and histamine liberaton were found. Pre-incubation of phagocytosing leucocytes with cytochalasin B or colchicine produced a diminution of PAF release, whereas beta-glucuronidase liberation was increased. The addition of carboxypeptidase B did not significantly modify PAF or beta-glucuronidase release. These data indicate that PAF obtained from preparations of human leucocytes comes from monocytes and polymorphonuclears; human basophils do not liberate measurable quantities of PAF, either by anaphylactic stimulus or by neutrophil cationic proteins; liberation of PAF and lysosomal content follow different mechanisms as they have different kinetics and are modified in an opposite way by drugs acting on the cytoskeleton.