Impact of irradiation on NK cell proliferation and homing in allogeneic BMT. A, Donor luc+ NK cells still proliferate when transplanted into unirradiated RAG2−/− γC−/− allogeneic recipients (lacking T, B, and NK cells) as measured by bioluminescence intensity. One representative animal for each group is shown over time. Groups consisted of three animals each and data are representative of two independent experiments. Days posttransplant are indicated along the top of the panels. B, Ex vivo imaging revealed trafficking patterns in the gastrointestinal tract of RAG2−/− γC−/− mice similar to irradiated, allogeneic recipients. Donor luc+ NK cells traffic to the mLN, spleen, and gastrointestinal tissue.