The microanatomy of calcium stores in human neutrophils: relationship of structure to function

As changes in cytosolic free Ca2+ play key roles in coupling responses in neutrophils, it is important to locate and identify Ca2+ storage sites within these cells. Here, recent data is presented which highlights the functional link between microanatomical structure and cell signalling function. Fluorescent optical probes for cytosolic free Ca2+ have been used, together with organelle specific markers. We present evidence from conventional fluorescence microscopy, together with ratiometric and confocal laser scanning fluorescence microscopy, which pin-points two cellular locations for Ca2+ within the neutrophil; one within the nuclear lobes, and the other towards the cell periphery. Knowledge of these two locations provides a clear insight into how signalling in this cell type is regulated and provides a framework for explaining how specific stimuli act to produce specific responses.