Suppression of Friend virus-induced leukaemia in mice by tuftsin

A significant decrease in mortality was observed when 25 micrograms of the tetrapeptide tuftsin was given to DBA/2J mice 5 days before infection with Friend leukaemia virus (FLV). The same effect was observed when tuftsin was given 5 days before and twice a week for 3 weeks after FLV infection. No effect was observed when the same amount of tuftsin was given 1 day before infection. A 5 micrograms dose of tuftsin given 5 days before and twice-weekly for 3 weeks had no effect on leukaemia induced by FLV infection. These findings showed that time and dosage were critical to the protective effect of tuftsin against virus-induced leukaemia.