INTRACELLULAR CONTROL OF HUMAN NEUTROPHIL SECRETION .1. C5A-INDUCED STIMULUS-SPECIFIC DESENSITIZATION AND EFFECTS OF CYTOCHALASIN-B

Abstract

Human neutrophils released the granule constituents myeloperoxidase and lysozyme, but not the cytoplasmic enzyme lactic dehydrogenase, when pretreated with cytochalasin B and stimulated with purified human C5a [fragment a of complement component 5]. Prior exposure to C5a before the cytochalasin B abrogated the subsequent secretory process. Interaction of neutrophils with C5a resulted in a concentration-dependent rapid desensitization that could not be overcome by later addition of cytochalasin B or of cytochalasin B and C5a. The effect was relatively stimulus-specific in that neutrophils desensitized in this manner could be induced to release granule enzymes by casein or by C-coated zymosan particles. Cytochalasin B effects on neutrophils appear to mimic those of surface binding of soluble stimuli such as C5a and immune complexes. Desensitization in concert with surface stimulation may represent an important intracellular mechanism for limiting neutrophil secretion.