Transient Graft-Versus-Host Reaction in the Treatment of Leukemia in Mice

Summary

Inbred RF mice, each bearing a transplanted myeloid leukemia, received 530 rads of X rays and then injections of C57BL spleen cells (10–60 × 10⁶) and bone marrow cells (40–60 × 10⁶). Most of these animals died with clinical and histological signs of secondary disease. Leukemia incidence, as judged by morphological criteria, varied with the spleen cell dose and ranged between 50% and 0. The severity of the secondary disease could be diminished, without recurrence of leukemia, by the immunosuppressive agents cyclophosphamide and heterologous antilymphocyte serum. Administration of recipient-type hematopoietic cells and blood after the course of cyclophosphamide abolished the chimeric state and prevented secondary disease, without recurrence of the leukemia. It is concluded that, in the experimental system used, permanent chimerism and the chronic graft-versus-host reaction are not necessarily prerequisite to the suppression of a transplanted leukemia.