Comparison of FcRγ-Deficient and CD57+ Natural Killer Cells Between Cord Blood and Adult Blood in the Cytomegalovirus-Endemic Korean Population

BACKGROUND FcRγ-deficient natural killer (NK) cells (g(-)NK cells) have been associated with cytomegalovirus (CMV) infection. However, the frequency of g(-)NK cells in a CMV-endemic area (i.e., Korea) has not yet been studied. We examined the frequency of g(-)NK cells and expression of CD57 on NK cells in cord blood (CB) and adult blood (AB). METHODS Of the 24 AB samples collected, 95.8% (23/24) were CMV IgG(+)/IgM(-), while 100% of the 13 healthy CB samples were CMV IgG(+)/IgM(-). We performed whole-blood flow cytometry assays to analyze intracellular FcRγ and CD3ζ expression of CD3(-)/CD56(dim) NK cells from 13 CB and 24 AB samples, and surface CD57 expression on CD3(-)/CD56(dim)/CD16(+) NK cells from 13 CB and 19 AB samples. RESULTS All CMV seropositive AB samples contained g(-)NK cells (23/23), and the median proportion of g(-)NK cells in the CD3(-)/CD56(dim) NK cell pool was 35.0% (range: 11-77%). CD57(+) NK cells in the CD3(-)/CD56(dim)/CD16(+) NK cell population were detected in all 19 AB samples tested, but not in any CB samples. CONCLUSIONS Our data suggest that g(-)NK cells and CD57(+) NK cells are present at a very high frequency in CMV-seropositive AB, but rare in CMV-naïve CB.