Engraftment of allogeneic bone marrow following administration of anti-T cell monoclonal antibodies and low-dose irradiation.

A nonlethal conditioning regimen involving administration of mAb in vivo, low-dose WBI and 700 rads of thymic irradiation, permits engraftment of T cell-depleted allogeneic BM. Engraftment of class I + II disparate allogeneic BM after conditioning with this regimen required depletion of both L3T4 and Lyt2 host T cell subsets in vivo. Treatment with a combination of specific mAbs to each subset (GK1.5 plus 2.43) was more effective than treatment with an anti-Thy1 mAb (30-H12). The low incidence of engraftment after 30-H12 treatment is probably due to reduced efficiency of 30-H12 in depletion of host alloreactive cell populations rather than an effect of this mAb on a particular population of donor cells that are important for engraftment.