PRF1 and neoplasm: The former is achieved by releasing granzymes and perforin or expressing death ligands (e.g., FasL and TRAIL), and the latter is mediated by secreting pro-inflammatory cytokines (e.g., IFNγ).367 NK cells do not express somatically rearranged T or B cell antigen receptors to specifically pick up tumor cells, instead, they target tumor cells with MHC class I-deficiency (missing-self signal) and/or stress-induced (e.g., DNA damage) activating ligand overexpression.