Parental-F1 Hybrid Bone Marrow Chimeras: High Incidence of Donor-Type Lymphomas

Adult LAF1 hybrid mice received a whole-body exposure to 500 R of X-rays, followed by a single intravenous injection of 4 × 106 normal, parental strain (A/He) bone marrow cells, which produced no overt graft-versus-host morbidity or mortality. On sacrifice, 2 years later, a striking increase in the incidence of malignant lymphoma (76%) over that of appropriate controls, was observed. Transplantation tests with cell suspensions prepared from these lymphomas revealed that they are of donor strain—rather than host—origin. The key point for lymphomagenesis here may be the persistent, tolerated histoincompatibility associated with the parental strain-F1 hybrid bone marrow cell chimerism, rather than immunosuppression by graft-versus-host reaction.