Degranulating stimuli decrease the neagative surface charge and increase the adhesiveness of human neutrophils

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Neutrophils (polymorphonuclear leukocytes [PMN]) exhibit decreased negative surface charge upon exposure to chemotactic factors, a phenomenon speculated to influence their behavior in vivo.
• PMN adherence and aggregation are known to be enhanced by the release of lysosomal enzymes during degranulation.

Purpose of the Study:

• To investigate the relationship between neutrophil degranulation, surface charge alterations, and changes in adherence and aggregation.
• To determine the role of extracellular ions (calcium and magnesium) in mediating these surface charge changes.

Main Methods:

• Human peripheral blood neutrophils were isolated using Hypaque-Ficoll and dextran sedimentation.
• Neutrophils were exposed to various secretagogues, including ionophore A23187, phorbol myristate acetate, concanavalin A, and chemotactic factors (C5a or f-met-leu-phe) with cytochalasin B.
• Surface charge was quantified using a cytopherometer, and lysozyme release was measured.

Main Results:

• Secretagogue-induced degranulation led to a greater decrease in PMN surface charge compared to chemotactic factors alone.
• The reduction in surface charge by f-met-leu-phe plus cytochalasin B required extracellular calcium and magnesium.
• Changes in surface charge correlated with lysozyme release and increased cell adhesiveness to plastic surfaces.

Conclusions:

• Exocytosis of lysosomal granule contents is associated with a decrease in neutrophil surface charge.
• A correlation exists between reduced surface charge and enhanced neutrophil aggregation and adhesiveness.
• The precise causal relationship between degranulation, surface charge reduction, and aggregation requires further investigation.