PLATELET-ACTIVATING FACTOR IN ANAPHYLAXIS AND PHAGOCYTOSIS .1. RELEASE FROM HUMAN PERIPHERAL POLYMORPHONUCLEARS AND MONOCYTES DURING THE STIMULATION BY IONOPHORE-A23187 AND PHAGOCYTOSIS BUT NOT FROM DEGRANULATING BASOPHILS

Abstract

Platelet-activating factor (PAF) is a mediator of anaphylaxis found initially in basophils and later in mouse and rat macrophages. The purpose was to determine the cellular origin of PAF released from human leukocytes and to establish if phagocytosis is a more important stimulus for PAF release than anaphylactic reactions. Phagocytic leukocytes (monocytes and PMN [polymorphonuclear neutrophils]) released PAF, physicochemically analogous to the PAF obtained by anaphylactic reactions in rabbits when challenged with zymosan, zymosan coated with complement, immune complexes, Ig aggregates or Ca ionophore A23187. Basophils failed to release PAF by anti-human IgE antibody, although positive degranulation and histamine liberation were found. Pre-incubation of phagocytosing leukocytes with cytochalasin B or colchicine produced a diminution of PAF release; .beta.-glucuronidase liberation was increased. The addition of carboxypeptidase B did not significantly modify PAF or .beta.-glucuronidase release. PAF obtained from preparations of human leukocytes apparently comes from monocytes and [PMN]; human basophils do not liberate measurable quantities of PAF 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.