Chemotactic factors decrease the negative surface charge of neutrophils (polymorphonuclear leukocytes [PMN]) and this has been speculated to be important in PMN margination and aggregation in vivo. PMN adherence and aggregation are also enhanced by degranulation of lysosomal enzymes. To further assess the possible relationship between degranulation, surface charge, adherence, and aggregation, human peripheral blood PMN (isolated by Hypaque-Ficoll and dextran sedimentation) were exposed to the secretagogues ionophore A23187, phorbol myristate acetate, concanavalin A, and chemotactic factors (partially purified C5a or the synthetic peptide f-met-leu-phe) plus cytochalasin B. Surface charge was measured in a cytopherometer. After incubation of PMN with secretagogues, PMN surface charge was decreased to a greater extent than incubation of PMN with chemotactic factors. The decreased surface charge induced by f-met-leu-phe plus cytochalasin B required both extracellular calcium and magnesium. The ionophore A23187-induced surface charge changes were dependent on extracellular calcium but not magnesium whereas the phorbol myristate acetate effect was only partially dependent on Ca++ and Mg++. The surface charge changes induced by secretagogues were related to both the amount of lysozyme released and to the increased adhesiveness of cells to plastic surfaces. These observations indicate exocytosis of lysosomal granule contents is associated with decreases in neutrophil surface charge, and there appears to be a correlation between decreases in surface charge and facilitation of neutrophil aggregation and adhesiveness. However, a causal relationship between these events has not been established, and the relationship may be simply temporal.
John I. Gallin