BM engraftment in congenic mice. A dose of 2×107 T cell depleted bone marrow cells from B6.CD45.1 mice was transplanted into CBA or congenic B6 mice treated with mAbs as described in figure 1. (A) One group of B6 mice was transplanted in the absence of any mAb treatment, and a group of CBA and B6 mice not subjected to BMT was used as a negative control. Hematopoietic chimerism was determined by quantification of peripheral blood mononuclear cells 120 days following BMT by flow cytometry. The results from two independent experiments are represented. The difference between the groups treated with mAb and any other group is statistically significant (p < 0.001). The difference between CBA and B6 recipients of B6.CD45.1 BM under the cover of mAbs is also significant in both experiments (p = 0.04 and p = 0.0006). (B) B6 mice were treated with 1 mg of the mAb PK136 administered 5 days prior to transplantation of B6.CD45.1 BM, to deplete their NK1.1 cells, while another group was treated with the control mAb YCATE55. Additional animals were subjected to the treatment described in Figure 1. NK cell depletion failed to achieve chimerism (p < 0.001).