CD4 and neoplasm: Through several interactions including TRAIL, NKp46 and yet to be defined receptors, NK cells can lyse CD4+ and CD8+ T cells resulting in less effective adaptive responses thereby promoting pathogen and tumor persistence (Lang et al., 2012; Waggoner et al., 2012; Cook and Whitmire, 2013; Peppa et al., 2013; Crouse et al., 2014; Schuster et al., 2014).