Rapid restoration of NK-cell numbers and function following irradiation and marrow grafting by IL-2 complex treatment. Irradiated bone marrow recipient mice (BMC mice) and (nonirradiated) B6 control mice were treated with IL-2 complex (IL-2C) on day 2 and day 4 after bone marrow transfer. (A) Spleen cells were analyzed on day 8 after bone marrow transfer and percentage of donor and host-derived cells, displayed in the histogram, was determined through congenic markers. (B) BrdU (2 mg) was injected intraperitoneally on day 5 after bone marrow transplantation, following treatment with IL-2 complex on day 2 and day 4. Animals were killed 10 hours after BrdU injection, and BrdU incorporation by NK1.1⁺CD3⁻ cells in the spleen was determined. (C) A mix of CFSE-low B6 and CFSE-high β2M^−/− splenocytes was transferred into control or B6 BMC mice and NK-mediated in vivo killing determined 48 hours later.