NK cells need an influx of calcium in order to operate.
When they are lacking CD16 the CD38 no longer will make the calcium go into the NK cells.
"CD16 :
It is a
cluster of differentiation molecule found on the surface of
natural killer cells,
neutrophil polymorphonuclear leukocytes,
monocytes and
macrophages.
[1]These receptors bind to the Fc portion of IgG antibodies which then activates the NK cell for
antibody-dependent cell-mediated cytotoxicity. A lack of CD16 in a given population of neutrophils may indicate prematurity, as could be caused by a
left shift due to neutrophilic leukocytosis induced by tissue necrosis or bacterial infection.
[2]"
So I don't know what would cause a lack of CD16 in NK cells, but as in the above paragraph, lack of CD16 in neutrophils has a listed cause. Although this paragraph may give another clue, lack of IgG antibodies on the NK cells.