Studies on cellular inhibition and serum-blocking factors in 28 human patients given marrow grafts from HLA identical siblings.

Fifteen patients with aplastic anemia and 13 with acute leukemia were studied 36 to 1547 days after treatment with high-dose cyclophosphamide and/or total-body irradiation and marrow transplantation from HLA identical siblings. Peripheral blood lymphocytes from patients and normals (marrow donors and healthy unrelated individuals) were tested for cell inhibition (CI) of cultured skin fibroblasts from both patients and donors by using the microcytotoxicity assay. In addition, blocking of CI by factors in patient serum was studied. Three groups of patients were studied. Patients in group I were stable long-term survivors without evidence of graft-vs-host diseases (GVHD) between 250 to 1547 days postgrafting. Patients in group II were short-term survivors with or without acute GVHD between 36 and 144 days postgrafting. Patients in group III had chronic GVHD either at the time of testing or developed chronic GVHD subsequent to CI testing between days 61 and 960 postgrafting. Eleven of 14 patients in group I showed absence of both CI and serum blocking and three showed CI and blocking. Patients in group II without acute GVHD showed absence of CI and serum blocking on three occasions, presence of CI and blocking on four occasions, and CI without blocking on three occasions. Patients in group II with acute GVHD showed absence of CI on one occasion and presence of CI and blocking on three occasions. Patients in group III showed absence of CI and blocking on seven occasions and CI without blocking on two occasions. These results suggest that the maintenance of stable graft-host tolerance in long-term survivors after marrow grafting from HLA identical donors does not depend on the presence of serum-blocking factors. Short-term survivors with and without GVHD showed a spectrum of in vitro reactivity with 50% of the patients showing serum-blocking factors, and these results did not appear to be correlated with presence or absence of acute GVHD. Finally, results of the microcytotoxicity assays failed to provide insight into the mechanism of chronic GVHD.