Malignant lymphoma and amyloidosis following graft-versus-host reaction.

Persistent stimulation of immunocompetent cells, such as histocompatibility reactions, may be one of the causes of neoplastic proliferation of lymphoreticular tissues. In the present studies, the graft-versus-host reaction was induced in 18week-old male ( C 57 Bl/6] x DBA/2 J )F1 mice · by two or four weekly intraperitoneal injections of approximately 80 x 106 male C 57 Bl/6 J or C 57 Bl/Na mouse lymphoid cells. Some of the recipient mice were treated with amethopterin. The majority of mice dying soon after injection of parental lymphoid cells showed signs of runt diesase and most animals recovering from the disease survived and were alive at the age of 24 months, at the termination of the experiments. Histological studies of 94 mice of experimental groups revealed lymphomatous changes in 10 mice and a moderate to extensive amyloidosis in 22 mice, with no abnormal changes in 15 untreated control mice. Nine out of 10 lymphomas were Type B, only one being reticulum cell sarcoma, Type A. Five out of 9 Type B lymphomas were associated with amyloidosis. Comparative analysis of mortality rates due to runt disease, and incidences of lymphoma and amyloidosis in each experimental group showed that the r esulting lymphoma incidences were apparently indifferent to the severity of runt disease. The results obtained in the present studies, together with those in others, suggest that the overt graft-versus-host reaction may not be a necessary precondition for increased lymphomagenesis in parental-Ft hybrid chimeras and that factors other tha.n the graft-versus-host reaction itself may also be involved.