CD16 receptors are mainly expresses on the surface of NK cells and mediate antibody-dependent cellular cytotoxicity (ADCC). The authors previously reported that NI< cell-mediated ADCC is influenced by the single nucleotide polymorphism (SNP) rs396991 (T > G; F158V), and the structure and expression levels of CD16 differed among these genotypes. The authors examined haplotype frequency distributions among rs396991 and other SNPs, rs10917571 (G > T), rs4656317 (C > G), and rs12071048 (G > A), located in an enhancer of the FCGR3A gene. A total of 101 healthy Japanese were genotyped for the presence of these SNPs. The authors also measured ADCC activity, FCGR3A transcript levels, and surface CD16 expression on NI< cells. We found that the regulatory SNPs (rSNPs) rs4656317 and rs12071048 were in strong linkage disequilibrium with rs396991. These two SNPs with major alleles had higher ADCC activity than those with minor alleles. In addition, FCGR3A transcript levels and surface CD16 expression levels were regulated by these SNPs. These findings suggest that NK cell-mediated ADCC could be influenced by transcriptional regulation of these rSNPs. These findings help to clarify our understanding of the linkage disequilibrium among functional SNPs in the FCGR3A gene, and provide a resource for investigating the roles of functional SNPs in NK cell-mediated ADCC. (C) 2016 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.