Host-derived IL-12 enhances survival following BMT Radiation chimeras were established by lethally irradiating (11 Gy) B6 Pepboy (C57BL6/J congenic, CD45.1) mice followed by transplant with 5 × 106BM Cells from either B6 (or BA – B6 congenic) or IL-12-p40 KO (B6 background) mice. Chimerism was confirmed a minimum of 50 days post-transplant by flow-cytometric analysis of congenic markers on total nucleated cells (CD45.1, CD45.2) for both B6 (A) and IL-12p40 KO (B) chimeras. Flow plots are data from one representative mouse per group. Chimeric mice were then conditioned with 9 Gy irradiation and transplanted with 5 × 106 FVB TCD BM cells along with 3 × 105 MACS-purified luc + FVB T-cells. A syngeneic transplant was also performed using non-radiation chimera FVB mice as recipients. Survival (C), percent weight loss from initial starting weight (D), and combined GvHD scores (E) were monitored after transplant. Data shown is combined from 3 independent experiments of 4–5 mice per group (WT and IL-12p40 KO) or 3 mice per group (syngeneic).