A, Representative cytometry plots showing the lack of CD16 expression by patient NK cells. B, CD16 expression on NK cells and monocytes of healthy, unrelated controls and family members. C, The structure of the low/medium- affinity FcγR locus on chromosome 1, compared with the same genomic region in the various members of the family studied. D, Low levels of CD16BA mRNA are found only in granulocytes of family members with this gene. MFI, Mean Fluorescence intensity; PMN, polymorphonuclear leukocyte.