Flow cytometric calcium flux assay: evaluation of cytoplasmic calcium kinetics in whole blood leukocytes

J Immunol Methods. 2009 Aug 31;348(1-2):74-82. doi: 10.1016/j.jim.2009.07.002. Epub 2009 Jul 16.


In leukocytes, as in many other cell types, cytoplasmic calcium ([Ca(2+)](i)) changes play a key role in a series of pathways leading to activation. Here we describe a flow cytometric method allowing the simultaneous kinetic analysis of changes in [Ca(2+)](i) in the three types of leukocytes, i.e. monocytes, granulocytes and lymphocytes. Heparinised whole blood was diluted in phosphate buffered saline with Ca(2+) and 1 mM sodium pyruvate and incubated with the Ca(2+) indicator fluo3-acetoxymethyl ester. Leukocytes were identified by labelling with the phycoerythrin-conjugated antibody against CD45, the leukocyte common antigen. Resuspension of the cells in PBS with or without Ca(2+) allowed us to detect the origin of Ca(2+) changes. During flow cytometric analysis only CD45-positive cells were counted and monocytes, granulocytes and lymphocytes were evaluated separately. Baseline fluorescence of the fluo3-Ca(2+)-complex was determined and changes in [Ca(2+)](i) after stimulation with the calcium ionophore A23187 or the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) were recorded over a time period of 150 s. Stimulation with A23187 resulted in a rise in [Ca(2+)](i) in all three leukocyte subpopulations. This rise was sustained in the presence of extracellular Ca(2+) (Ca(2+)(ex)) but had a transient character in the absence of Ca(2+)(ex). For fMLP, [Ca(2+)](i) changes occurred only in monocytes and granulocytes and were transient irrespective of the presence or absence of Ca(2+)(ex). In conclusion, the present method is a simple, fast and easy tool to analyse in vitro [Ca(2+)](i) changes over time in leukocytes under physiologically relevant conditions, without the need for their isolation or the lysis of erythrocytes. The whole blood approach allows a continuous interaction between the different leukocyte subpopulations and other blood components and a minimum of preparative manipulations avoids artefactual activation of the cells. A distinction can be made between Ca(2+) release from the intracellular stores and the entry of Ca(2+) from outside the cell. The approach allows to evaluate the effect of various agonists on [Ca(2+)](i) changes in leukocytes, with physiological, patho-physiological or therapeutic purposes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aniline Compounds / pharmacology
  • Calcimycin / pharmacology
  • Calcium / agonists
  • Calcium / analysis*
  • Calcium Signaling*
  • Flow Cytometry / methods*
  • Fluorescent Dyes / pharmacology
  • Humans
  • Kinetics
  • Leukocyte Common Antigens / metabolism
  • Leukocytes / drug effects
  • Leukocytes / metabolism*
  • N-Formylmethionine Leucyl-Phenylalanine / pharmacology
  • Xanthenes / pharmacology


  • Aniline Compounds
  • Fluorescent Dyes
  • Xanthenes
  • Fluo-3
  • Calcimycin
  • N-Formylmethionine Leucyl-Phenylalanine
  • Leukocyte Common Antigens
  • PTPRC protein, human
  • Calcium