The ex vivo incubation of donor BALB/c BM with serum from BALB/c-primed B6 mice results in the destruction of the antibody-coated donor BM cells in a nonprimed B6 recipient. (A) Serum was collected from naive or BALB/c-primed mice, diluted 1:20, and incubated with BALB/c or BR BM. BM was thoroughly washed. An aliquot was incubated with FITC-conjugated goat anti–mouse Ig Ab and analyzed by flow cytometry. Histograms indicate binding of serum alloantibody to BALB/c or BR BM. Negative control of FITC-conjugate binding to BM in absence of serum is indicated by the thin dotted line. (B) Nonprimed B6 mice were lethally irradiated (8.0 Gy) and infused with BALB/c or BR BM cells (10 × 10⁶) that had been incubated with serum from naive or BALB/c-primed B6 mice as shown in panel A. Survival is shown. n = 8 to 10/group; BALB/c BM incubated with naive versus BALB/c-primed serum, P = .003. Results were reproduced in a second experiment.