Cytotoxic effector cells with the characteristics of natural killer cells in the lungs of mice

Cells with in vitro cytotoxicity against tumor targets in a short-term 51Cr release assay have been recovered from the lungs of mice that were either untreated or injected with biological or synthetic agents 1-3 days earlier. The cytotoxic effector cells were non-adherent, non-phagocytic and shared many characteristics with splenic natural killer (NK) cells. This finding is discussed with particular regard to our previous observations on the rapid in vivo elimination from the lungs of intravenously injected, radiolabelled tumor cells.