Lidocaine inhibits macrophage mediated cytotoxicity and enhances neutrophil mediated cytotoxicity.

Peripheral blood monocyte derived macrophages and polymorphonuclear leukocytes (PMNs) obtained from normal donors kill tumor cells in vitro. However, if lidocaine is added to the macrophage tumor cell suspensions in microgram concentrations (0.1 micrograms-0.1 mg), there is marked inhibition of tumor cell killing. The inhibitory effect for the macrophages resulted from an effect of lidocaine on the effector cells. When the effector cells were preincubated with lidocaine, inhibition in macrophage mediated cytotoxicity was observed. Cytotoxicity was also inhibited when 0.01 mg of lidocaine was added to the macrophage monolayers either at the time of addition of the tumor cells or 15-60 min after addition of the tumor cells whereas no inhibition of cytotoxicity occurred when lidocaine was added more than 60 min after the initiation of the cytotoxic reaction. For the neutrophils it was observed that the lidocaine actually had an enhancing effect rather than inhibitory effect on their ability to kill tumor cells.