Evidence that anti-asialo GM₁ in vivo improves engraftment of t cell-depleted bone marrow in hybrid recipients

Engraftment of T cell-depleted bone marrow was studied in a P-F₁ murine bone marrow transplant model which features long-term stability of mixed chimerism of donor (B6) and host (B6AF1) cells after BMT. We report that a polyclonal antibody to asialo GM₁ (anti-ASGM₁) given in vivo after transplant was able to increase long-term donor bone marrow engraftment. In vivo anti-ASGM₁ eliminated NK activity but did not affect the generation of cytotoxic T cells nor did it stimulate hematopoiesis in vitro. Anti-Thy 1.2, a pan- T cell monoclonal antibody, had no effect on donor en- graftment. We conclude that ASGM₁⁺ cells with NK activity inhibit the long-term engraftment of bone marrowstem cells in this model and that antibodies to NK cells can be used in vivo as an effective component of the transplant conditioning regimen.