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Updated: Aug 13, 2026

Examination of Thymic Positive and Negative Selection by Flow Cytometry
Published on: October 8, 2012
Calcium oscillations regulate thymocyte motility during positive selection in the three-dimensional thymic
Nirav R Bhakta1, David Y Oh, Richard S Lewis
1Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA.
Abstract:
The three-dimensional thymic microenvironment and calcium signaling pathways are essential for driving positive selection of developing T cells. However, the nature of calcium signals and the diversity of their effects in the thymus are unknown. We describe here a thymic slice preparation for visualizing thymocyte motility and signaling in real time with two-photon microscopy. Naive thymocytes were highly motile at low intracellular calcium concentrations, but during positive selection cells became immobile and showed sustained calcium concentration oscillations. Increased intracellular calcium was necessary and sufficient to arrest thymocyte motility. The calcium dependence of motility acts to prolong thymocyte interactions with antigen-bearing stromal cells, promoting sustained signaling that may enhance the expression of genes underlying positive selection.
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