Cimetidine enhances interferon induced augmentation of NK cell activity and suppresses interferon production

Effects of cimetidine on the augmentation of natural killer (NK) cell activity by human leukocyte interferon (Hu IFN-alpha (Le] and on the IFN production from donor leukocytes were investigated in vitro. NK cell activity of PBL was suppressed after 16 hours pretreatment with 0.3, 3.0, and 30.0 micrograms/ml of cimetidine. On the other hand, there was dose dependent suppression of Hu IFN-alpha (Le) production in PBL by cimetidine. The NK cell activity of PBL augmented by Hu IFN-alpha (Le) was further enhanced when the effector cells were pretreated with cimetidine or when cimetidine was added together with IFN. K562, G361, and PLC/PRF/5 cells were used as target cells. Our results suggest that a 16 hour treatment with cimetidine alone may suppress NK cell activity of PBL, probably due to reduced IFN production by leukocytes. On the other hand, cimetidine may enhance the IFN induced NK augmentation in PBL in vitro.