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 engraftment. We conclude that ASGM1+ cells with NK activity inhibit the long-term engraftment of bone marrow stem cells in this model and that antibodies to NK cells can be used in vivo as an effective component of the transplant conditioning regimen.