NKD1 and gastric cancer: Similar to NK cells, NK T cells and γδ T cells use cell-surface receptors to recognize tumors.7,8 It has been suggested that NK cells could modulate TILs.9,10 Germline mutations often lead to both NK deficiency (NKD) and Epstein-Barr virus–associated diseases.11 Further, EBV is a key risk factor for gastric cancer; almost 10% of gastric cancer cases are associated with EBV.12 Thus far, 45 NKD genes,13 such as GATA2 (OMIM 137295),11,12GINS1 (OMIM 610608),6IRF8 (OMIM 601565),5MCM4 (OMIM 602638),7,8RTEL1 (OMIM 608833)14 and FCGR3A (OMIM 146740),15,16,17 have been clinically determined.