After eight years of work, researchers have unearthed what has been a well-kept secret of our immune system's success. The findings published online on June 9th in Immunity, a Cell Press publication, offer an explanation for how specialized immune cells are able to kill infected or cancerous cells without killing themselves in the process. The focus of the study is a molecule known as perforin, whose job it is to open up a pore in cells targeted for destruction. With that pore in place, proteases known as granzymes can enter target cells and destroy them. Perforin is one of the...