Analysis of subcellular calcium signals in T-lymphocytes

Subcellular Ca2+ signals were analysed in Jurkat and peripheral human T-lymphocytes by confocal Ca2+ imaging employing an off-line deconvolution method. Stimulation of the TCR/CD3 complex in T-lymphocytes resulted in a series of subcellular pacemaker Ca2+ signals preceding the first global Ca2+ signal. The pacemaker signals occurred in a cytosolic "trigger" zone, which is localised close to the plasma membrane. The pacemaker signals were almost independent of extracellular Ca2+ as shown by measurements in the absence of extracellular Ca2+, or in the presence of the Ca2+ channel blocker SK-F 96365. Analysis of the confocal Ca2+ images revealed characteristic amplitudes of 82 +/- 30 to 109 +/- 21 nM, signal diameters between 2.5 +/- 0.9 and 3.5 +/- 1.5 mum and frequencies between 0.235 and 0.677 s(-1). Taken together, our data constitute the first analysis of subcellular Ca2+ signals in T cells and indicate that the pacemaker Ca2+ release events, which are necessary for the development of the global Ca2+ signal, are composed of Ca2+ release both from inositol 1,4,5-trisphosphate- and ryanodine receptors. (C) 2003 Elsevier Science Inc. All rights reserved.