Ziram is a currently used agricultural fungicide. It is also used as an additive in the production of
latex gloves. Because of these uses, there is a potential for human exposure to this compound.
Pentachlorophenol (PCP) has been used as an
insecticide, fungicide,
disinfectant, and ingredient in antifouling paints. Currently, it is used as a wood preservative for power-line poles and fence posts. Measurable levels of PCP have been detected in human blood and urine. In previous studies we demonstrated that both these compounds could cause very significant inhibition of the
tumor-killing function of human natural killer (NK) cells. NK lymphocytes play a central role in immune defense against
viral infection and the formation of primary
tumors. So interference with their function could increase the risk of
tumor development. In the present study we examined the effects of exposure to
ziram or PCP of brief duration (1 h) on the ability of NK cells to destroy
tumor cells. NK cells were exposed to either
ziram (5-0.5 microM) or PCP (10-5 microM) for 1 h followed by 0 h, 24 h, 48 h, or 6 days in compound-free media and then were tested for the ability to lyse as well as to bind
tumor cells. A 1-h exposure to as little as 2.5 microM
ziram decreased the ability of NK cells to lyse target
tumor cells, which persisted up to 6 days following exposure. The loss of lytic function for from 24 h to 6 days following exposure was accompanied by a comparable loss of NK capacity to bind
tumor cells. Exposure to 10 microM PCP for 1 h caused a progressive loss (greater than 80%) of lytic function within 6 days of exposure. In contrast to
ziram, PCP exposure caused no accompanying loss of binding function.