The human protein perforin is central to 'immune surveillance' whereby white blood cells patrol the body. These 'natural killer' cells use perforin to deliver a signal to virally infected and potentially cancerous cells, causing them to initiate a suicidal response. Researchers in the Division of Structural Biology studying perforin have discovered that in addition to forming pores in cell membranes, the protein can cause a unique form of 'endocytosis' (cell eating) whereby the suicidal signal is taken inside target cells without damaging the outer cell membrane.
Read more: http://www.pnas.org/content/early/2011/12/09/1107473108.full.pdf+html