Immune complex stimulation of human neutrophils involves a novel Ca2+/H+ exchanger that participates in the regulation of cytoplasmic pH: flow cytometric analysis of Ca2+/pH responses by subpopulations

The activation of human phagocytic leukocytes by immune complexes (IC) or opsonized microbes via their Fc and complement receptors has been well‐described (for reviews, see refs. [123]). The mechanisms involved in this process are complex and depend on the receptors involved. The biochemical events that lead to the destruction of invading organisms in turn display varying degrees of interdependence, but the controlling elements that lead to the ultimate killing of ingested organisms within phagosomes by lysosomal enzymes and reactive oxygen intermediates are still not completely understood. We have addressed these mechanisms by following and correlating the kinetics of responses by individual cells, using multiparameter flow cytometry [34]. Using nonopsonized IC as stimuli, we document here the presence of a novel Ca2+/H+ voltage‐independent channel in human neutrophils, which helps to control their cytoplasmic pH.