Columbia University Irving Medical Center A newly discovered fat “shield” that prevents natural killer cells from being destroyed by their own deadly biological weapons also allows some cancer cells to evade an immune system attack, a study at Columbia University has found. The findings, which may lead to new treatments for aggressive cancers, were reported Aug. 3 in the journal PLoS Biology by scientists in the Department of Pediatrics at Columbia University Vagelos College of Physicians and Surgeons. A 3-dimensional model of a natural killer cell (purple) with granules (yellow) attaching to a target cell (gray). A pseudocolor scale shows differences in packing density of lipids on the natural killer cell membrane, with warmer colors indicating higher density. (Orange laboratory)