Platelets have roles in blood clotting and inflammation, and may also be required for the interaction between the 'sentinel' cells of the immune system and certain blood-borne bacteria.
Admar Verschoor and Dirk Busch at the Technical University of Munich in Germany and their colleagues monitored infection by the bacterium Listeria monocytogenes in mice. They found that platelets clustered around the bacteria, shuttling them to the spleen, where immune cells called dendritic cells engulf the pathogen. These are the first steps to mounting an immune response involving cell-killing T cells. The authors identified a key immune-system protein and a platelet receptor that are necessary for the association of platelets with L. monocytogenes, as well as with other clinically relevant bacteria.
Nature Immunol. http://dx.doi.org/10.1038/ni.2140 (2011)