Heterogeneity in the mobilization of cytoplasmic calcium by human polymorphonuclear leukocytes in response to fMLP, C5a and IL-8/NAP-1

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Abstract
The visible excitation and emission wavelengths of the recently developed fluorescent Ca2+ indicator fluo-3 permit analysis of the intracellular Ca2+ concentration, [Ca2+]i, in flow cytometry with a 488-nm argon laser. The role of [Ca2+]i in human polymorphonuclear leukocyte heterogeneity was investigated in response to formyl-methionyl-leucyl-phenylalanine (fMLP), C5a, and interleukin 8/neutrophil attractant/activation protein 1 (IL-8/NAP-1) by flow cytometry. The [Ca2+]i changes in different subpopulations within a heterogeneous cell suspension were resolved upon stimulation with fMLP. Using an anti-CD16 phycoerythrin-conjugated antibody and fluo-3 simultaneously, neutrophils affected and nonaffected in Ca2+ mobilization were distinguished in two patients suffering from glycogen storage disease type lb. In normal neutrophils, a different time course of Ca2+ mobilization of neutrophil subpopulations immediately after stimulation with fMLP was detected. In addition, after stimulation with a low concentration of IL-8/NAP-1 (10-10 M) two subsets of neutrophils appeared; one of them showed an increase in [Ca2+]i, while the other did not. These results indicate heterogeneity in the neutrophil signal transduction process involved in Ca2+ mobilization. Therefore, flow cytometric analyses can resolve changes in single-cell [Ca2+]i distribution patterns, which is important for the understanding of [Ca2+]i in neutrophil heterogeneous activation processes.

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