Inhibitory effect of diazepam on human natural killer activity in vitro

The in vitro effect of diazepam on natural killer (NK) cell activity isolated from human peripheral blood has been investigated. NK cell function was estimated by means of a radioactive chromium (51Cr) assay in which human erythroleukaemia K562 cells were used as the target. Diazepam suppressed NK cell function in a concentration-dependent manner (10(-7)-10(-5) M) and a positive correlation was found between the dose of diazepam and inhibition detected by percentage killing of K562 cells. These data indicate that diazepam influences cytotoxic activity and diminishes anti-viral and anti-tumour defence reactions in humans.