Natural killer cell granules converge to avoid collateral damage

To clear infection, cytotoxic lymphocytes must destroy target cells while avoiding nonspecific killing of surrounding healthy cells. In this issue, Hsu et al. (2016. J. Cell Biol. https://doi.org/10.1083/jcb.201604136) use live-cell imaging to show that lytic granule convergence protects bystander cells from unintended death by promoting polarized secretion of soluble cytolytic proteins toward the intended target.