Lymph node morphology after allogeneic bone marrow transplantation for chronic myeloid leukemia: a histological and immunohistological study focusing on the phenotype of the recovering lymphoid cells.

A histological and immunohistological analysis of lymph nodes after allogeneic bone marrow transplantation (BMT) was performed to investigate the microarchitecture of the lymphatic tissue and the phenotype of the recovering lymphoid cells. The study included four patients with chronic myeloid leukaemia who had died between 0.5 and 12 months after transplantation. The study yielded the following results: 1. All lymph nodes, irrespective of length of the survival period, exhibited severe atrophy of the lymphoreticular tissue with marked depletion of lymphocytes and dilatation of the sinuses. The number of lymphoid cells increased considerably with time after transplantation. 2. The main constituents of the recovering immune system were mature T lymphocytes (CD4+ and CD8+ cells in nearly equal numbers) and macrophages. The earliest signs of recovery of the immune system could already be detected 0.5 month after BMT. 3. Extreme paucity of B lymphocytes was a prominent finding in all lymph nodes studied. True lymphatic follicles and germinal centres were never detected. 4. Polytypic plasma cells were seen in low or moderate numbers mainly in the lymph node sinuses, while neither marked plasmacytic hyperplasia nor even a monotypic pattern were found. 5. Immune-accessory reticulum cells were detected only in the lymph nodes of the patient who survived 12 months. 6. Natural killer cells occurred only in low numbers irrespective of the duration of survival after BMT. Altogether, the histopathological lymph node findings clearly reflect the marked long-standing depression of the immune responses seen after allogeneic bone marrow transplantation. Since three of the four patients had shown signs of acute or chronic graft-versus-host disease, the histological findings presumably do not fully reflect the normal reconstitution of the immune system, but may have been modified by phenomena related to graft-versus-host disease.