Anti-human-thymocyte globulin (AHTZG) was applied to prevent GvHD in clinical bone marrow transplantation. AHTZG produced by absorption with several cell preparations reacted specifically with T-lymphocyte populations and was no longer inhibitory to human CFUc and bone marrow growth in diffusion chambers. Marrow grafts of 14 patients with ALL were incubated in vitro with AHTZG and transferred to the recipients conditioned with antileukemic chemotherapy and total body irradiation of 1000 rad. Ten patients were transplanted after relapse, four patients during remission. The patients tolerated the marrow without side effects and a hemopoietic engraftment was seen in 12 cases. Three patients showed signs of GvHD on the skin, two of them showed later on also manifestations in the liver. In the other cases no GvHD could be detected. Five out of 14 patients are still alive between 144 and 964 days post transplantation in remission.
