RESUMO
Cytotoxic function of human natural killer (NK) cells is modulated by a variety of cytokines. Interleukins (IL) 2, 12, 15, and 18 and Interferon gamma (IFNgamma) are potent stimulators of NK cell cytotoxicity. Butyltins (BTs) are used in a variety of consumer products and industrial applications. Dibutyltin (DBT) is found in plastic products, beverages stored in PVC pipes during manufacturing, and poultry products. BTs appear to increase the risk of cancer and viral infections in exposed individuals. Recently, we have demonstrated that the ability of NK cells to kill tumor cells is greatly diminished after a 1-h exposure to dibutyltin. This inhibition of tumor killing function continues even after removal of the compound. There is no significant recovery of NK cytotoxic function even when the cells are allowed to recover for 6 days. In the current study we examine the effects of NK-stimulatory cytokines on the ability of NK cells to recover from the inhibitory effects of a 1-h DBT treatment. Highly purified NK cells (>95% CD16(+)) or a lymphocyte preparation containing both T lymphocytes and NK cells were treated with 5 microM DBT and then allowed to recover for 24 h, 48 h, 4 days, and 6 days in DBT-free medium containing either no cytokine or a maximally stimulatory dose of several NK-stimulatory cytokines. Tumor killing function was tested using a radioactive chromium release assay. As seen in our previous studies there is no recovery of NK cell cytotoxic function even after a 6-day recovery period when no cytokine is present in the medium. However, there is significant recovery of NK cytotoxic function when IL2, IL12, or the combination of IL2 plus IL12 is present in the medium during the recovery period. The other cytokines tested (IL15, IL18, and IFNgamma) were unable to increase the cytotoxicity of DBT-exposed NK cells.
