IL21 and esophageal squamous cell carcinoma: As it has been reported that CD247 molecules (signal-transducing ζ molecules) on NK cells were related to CD16 (Fc receptor)-related cytotoxicity (Whiteside, 2004), we evaluated the expression of CD247 molecules on NK cells (CD56(+)CD3(−)), analysed by intracellular staining with flow cytometry, when PBMCs in patients with ESCC were treated with IL-21.