Human natural killer (NK) cells are central in immune defense against
tumor and virally infected cells.
Ziram is used as an accelerating agent in
latex production and as an agricultural fungicide. Previous studies showed that continuous exposure to
ziram inhibits NK lytic function. Additionally, they showed that a brief (1 h) exposure to
ziram caused persistent loss of lytic function. This study examined whether decreases in lytic function were accompanied by decreases in the target-binding function of NK cells and found that some, but not all, exposures to
ziram caused significant decreases in binding function.
Ziram exposures that caused a loss of binding function were examined for effects on expression of key NK cell-
surface proteins needed for binding to targets. Exposure to 2 microM
ziram for 1 h followed by 24 or 48 h in
ziram-free media decreased CD16 expression, but no other exposures caused decreases in
cell-surface proteins. As decreases in
adenosine triphosphate (
ATP) could be in part responsible for loss of lytic function, the effect of
ziram exposures on
ATP levels of NK cells were examined. Certain
ziram exposures decreased
ATP levels in NK cells, but a decrease in
ATP was not necessarily associated with a decrease in lytic function. The results indicate that
ziram-induced losses of lytic function cannot be fully explained by alteration in binding,
cell-surface protein expression, or
ATP levels.