Cytotoxic T lymphocytes (CTLs) are immune cells that destroy the structural integrity of virus-infected or cancer-causing cells by releasing toxic granules into them. At the point of contact between the CTL (distinguished by CD8 protein dyed white) and its target cell an immunological synapse (shown as bright green) is created, through which the cells interact (cell nuclei dyed blue). Inside cells a structure called the centrosome (coloured red), where the cell’s skeletal elements are made, is responsible for moving granules to the right place. Brought to the synapse in a CTL (right-hand image) the centrosome ensures that the toxic granules will hit their intended target when the immune cells dock onto diseased cells. Biologists have found that Lck, a protein within the CTL, is vital for centrosome docking (right image). When the centrosome fails to move to the synapse, docking is unsuccessful (left), and diseased cells cannot be discarded.
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