Handing over the baton

Cells generally communicate with one another through either soluble or membrane-bound mediators that bind to receptor proteins at the plasma membrane of the receiving cell. Thus, in most cases the plasma membrane acts as the last boundary that separates the cell's proteins from the extracellular milieu. However, 36 years ago it was noted that cells contain proteins that have been acquired from their neighbours,1 and this phenomenon has consistently been confirmed ever since.2, 3 In a recent issue of the Proceedings of the National Academy of Science USA, Parish and colleagues4 describe that T cells can transfer their T-cell receptor (TCR) to bystander T cells of unrelated specificity to help clear viral infections, thus introducing a level of promiscuity in non-clonally selected cells that was previously unthinkable.