Cytotoxic (killer) T cells use an unexpected mechanism to deliver their deadly cargo to target cells.

Cytotoxic T cells are the hired assassins of the immune system. They attach to cells infected by a virus and release a volley of proteins that destroy the infected cell. Gillian Griffiths and colleagues at the University of Oxford have now discovered how these cells deliver this 'kiss of death'.

The T cells store cytotoxic chemicals in special compartments, lytic granules. When a T cell recognises an infected cell, the granules are transported along microtubules, the railway tracks of the cell, which become oriented towards the point of contact with the target cell.

But, Professor Griffiths's group has discovered, the final secretory step uses a novel mechanism to deliver the lethal hit. A structure known as the centrosome, which forms the organising centre for microtubules, makes direct contact with the T-cell membrane at the point of contact with the doomed target cell.

Image courtesy of JC Stinchcombe and GM Griffiths.

External links

• Stinchcombe JC et al. Centrosome polarization delivers secretory granules to the immunological synapse. Nature 2006;443(7110):462–5.