Effect of lidocaine on natural killer activity: rapid inhibition of lysis.

We have previously found that NK cell activity is present in rat lung lavage and inhibited by lidocaine. The purpose of this report is to characterize further the inhibition by lidocaine on NK activity. Peripheral blood lymphocytes from normal human volunteers were assayed in a four-hour 51chromium release assay in the presence of varying concentrations of lidocaine during or prior to the lytic assay. During the assay, increasing concentrations of lidocaine inhibited NK activity. This effect was not related to pH and at high concentrations was unrelated to methylparaben found in topical lidocaine. Preincubation of effector cells for one hour with different concentrations of lidocaine produced similar results which were temperature dependent and related to incubation time. Preincubation of effector cells in lidocaine (0.5g%) for one to ten minute intervals at 37 degrees C resulted in 60 to 92% inhibition, respectively. The lidocaine did not alter effector cell viability nor did it affect the phenotypes of the effector cells as determined by flow cytometry. Lidocaine's inhibition of NK activity remained the same for cells which were further purified by plastic adherence, nylon wool filtration and percoll density centrifugation. The effect was not reversed by a 16 hour incubation in tissue culture medium. In a single cell assay, we determined that the inhibition was at the level of cell lysis.