In vitro inhibition of natural killer cell activity by doxycycline

The effect of four tetracyclines, tetracycline, rolitetracycline, oxytetracycline and doxycycline, on human natural killer (NK) cell-mediated cytotoxicity was examined in vitro. Doxycycline was the only tetracycline which inhibited the NK cell activity. At concentrations of 10 micrograms/ml the drug caused approximately 50% inhibition of NK cell mediated cytotoxicity against K562 target. The inhibition was not a result of a toxic effect of the drug on NK cells. These results support the previous findings that doxycycline shows immunosuppressive properties.