Analysis of subcellular calcium signals in T-lymphocytes

Abstract

Subcellular Ca 2+ signals were analysed in Jurkat and peripheral human T-lymphocytes by confocal Ca 2+ imaging employing an off-line deconvolution method. Stimulation of the TCR/CD3 complex in T-lymphocytes resulted in a series of subcellular pacemaker Ca 2+ signals preceding the first global Ca 2+ 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 Ca 2+ as shown by measurements in the absence of extracellular Ca 2+, or in the presence of the Ca 2+ channel blocker SK-F 96365. Analysis of the confocal Ca 2+ images revealed characteristic amplitudes of 82±30 to 109±21 nM, signal diameters between 2.5±0.9 and 3.5±1.5 μm and frequencies between 0.235 and 0.677 s −1. Taken together, our data constitute the first analysis of subcellular Ca 2+ signals in T cells and indicate that the pacemaker Ca 2+ release events, which are necessary for the development of the global Ca 2+ signal, are composed of Ca 2+ release both from inositol 1,4,5-trisphosphate- and ryanodine receptors.