Shuttling bacteria

Platelets are important for driving the immune response towards bacteria, reports a study published online this week in Nature Immunology.

The classical role for platelets has been their involvement in blood clotting reactions. However, Dirk Busch and colleagues show that certain types of bacteria in the blood are very rapidly coated in platelets and this process depends on a platelet-expressed molecule called GPIb. This directs bacteria to the spleen where they are engulfed by dendritic cells — cells that play a key role in initiating a full-blown immune response. Failure to coat bacteria in platelets routes them instead to another cell type, the macrophage, which destroy the bacteria but does not allow the generation of immunological memory.