The MHC background does not modify the behavior of adoptive transferred mature NK cells in alymphoid Rag°γ_c° recipient mice. (A) CFSE dilution profiles of splenic NK cells 3 days after adoptive transfer into the indicated hosts. An electronic gate was set on CD122⁺ (IL-2Rβ⁺) cells. Boxes in NK1.1 profiles correspond to CFSE⁺ NK cells that have not divided. For different Ly49s, percentages of the relevant subset are indicated. (B) Absolute numbers of recovered splenic CD122⁺NK1.1⁺ NK cells at 3 days after transfer. Black bars (▪) indicate nondivided donor NK cells and open bars (□) indicate NK cells with more than one division. Error bars denote standard deviations.