CYTOKINE PRIMING OF THE RESPIRATORY BURST IN HUMAN EOSINOPHILS IS CA2-ACTIVITY( INDEPENDENT AND ACCOMPANIED BY INDUCTION OF TYROSINE KINASE)

We report that pretreatment of human eosinophils with GM-CSF, IL-3, or IL-5 enhanced the respiratory burst induced by opsonized particles. I n order to gain more insight into the intracellular mechanism(s) invol ved in cytokine priming, the role of [Ca2+]i and tyrosine kinases was studied. Optimal priming concentrations of GM-CSF, IL-3, and IL-5 did not induce a rise in [Ca2+]i, and Ca2+-depleted eosinophils ([Ca2+]i < 20 nM) were still primed after preincubation with these cytokines. GM -CSF, IL-3, and IL-5 induced phosphorylation of two proteins (102 and 122 kd) on tyrosine residues, as deduced from Western blot analysis wi th an antiphosphotyrosine monoclonal antibody (4G10). This cytokine-st imulated tyrosine phosphorylation was not inhibited under Ca2+-deplete d conditions. In conclusion, this study demonstrates that GM-CSF, IL-3 , and IL-5 priming of the opsonized particle-induced respiratory burst in human eosinophils is completely Ca2+ independent. Moreover the tyr osine phosphorylation of a 102-kd and a 122-kd protein is Ca2+ indepen dent, suggesting that this event might be involved in cytokine priming .