A highly focused laser beam (at right) is used to apply mechanical force (shown as a double headed arrow) to a microsphere (white) coated with histocompatibility protein. The microsphere abuts the surface of a single T cell, shown in gray (top). Activation of the T cell is measured by a change in calcium levels within the cell, which are shown by green colorization (left, prior to force application; bottom, after force application). The direction of force must be tangential, rather than perpendicular, to the T cell surface in order to trigger a rise in calcium levels. Without an application of force, the binding of the histocompatibility protein produces no such rise. (Credit: Please credit Dana-Farber Cancer Institute)From Science Daily:
Science Daily (Nov. 10, 2009) — The immune system's T cells have the unique responsibilities of being both jury and executioner. They examine other cells for signs of disease, including cancers or infections, and, if such evidence is found, rid them from the body. Precisely how T cells shift so swiftly from one role to another, however, has been a mystery.
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