Abstract
Soluble immune complexes activate a rapid burst of reactive oxidant secretion from neutrophils that have previously been primed with GM-CSF. Binding of these complexes to the cell surface of unprimed neutrophils results in the generation of intracellular Ca 2+transients, but the NADPH oxidase fails to become activated. No phospholipase D activity was observed following the addition of soluble immune complexes to unprimed cells. Upon priming with GM-CSF, the intracellular Ca 2+signal generated following soluble complex binding was greatly extended and phospholipase D was activated: there was also increased phosphorylation of proteins on tyrosine residues and the NADPH oxidase was activated. When Ca 2+influx was prevented, this phospholipase D activity was not observed. This primed oxidase activity was completely inhibited by erbstatin. Treatment of unprimed neutrophils with pervanadate (to inhibit protein tyrosine phosphatases) mimicked the effects of priming in that pervanadate-treated neutrophils secreted reactive oxidants in response to soluble immune complexes. The data indicate that during priming a new signaling pathway is activated that involves Ca 2+influx, phosphorylation on tyrosine residues, phospholipase D activity, and NADPH oxidase activation.
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