Generation of NK cells.

(A) Flow cytometric analysis of wild-type C57Bl/6 spleen cells andRAG2cγ^−/−spleen cells 3 months after reconstitution with a Pax5^−/−pre-B I–cell clone. (B) Cytotoxicity assay. NK1.1⁺CD3⁻ cells were sorted from C57Bl/6 spleen (●), and reconstitutedRAG2cγ^−/− (○) were activated for 7 days in vitro with IL-2 and then assayed for their cytotoxicity against YAC-1 and lipopolysaccharide-stimulated spleen cells of β2m^−/− mice.