Directional secretion of lytic granules could serve to protect healthy tissue. (A) NK cells (brown) may identify targets (yellow) that reside in tissues surrounded by healthy bystander cells (teal). (B) Convergence of lytic granules (red) and polarization of the MTOC to the target cell interface encourages directional secretion of granules toward the target. Concentration of secreted cytolytic proteins in the synaptic cleft enhances target killing efficiency and prevents destruction of bystander cells. (C) Lack of a granule convergence signal leads to nondirectional secretion and possible collateral damage to tissue.