Lymphomagenesis and autoimmunization caused by reactions of T-lymphocytes to incompatible structures of the major histocompatibility complex: a concept of pathogenesis

Graft-versus-host reactions: clues to the etiopathology of a spectrum of immunological diseases

Parental strain T lymphocytes injected into adult F, mice respond to allogeneic MHC antigens and so induce the symptoms of systemic graft v. host disease (GVHD). GVHD has two forms, stimulatory and suppressive, and in each there are pathological changes which resemble those seen in a variety of human disorders of immune regulation. In this article Ernst Gleichmann and his colleagues review the pathogenesis of these disorders and their induction by GVH reactions.

Second malignancies after allogeneic hematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) may prolong life and cure patients suffering from otherwise fatal diseases. However, the growing population of long-term survivors has led to the realization of multiple long-term complications, including the risk of second malignancies. Compared to the autologous setting, allo-HCT carries a much higher risk of posttransplant lymphoproliferative disorder (PTLD), which usually occurs within the first year after allo-HCT and is strongly associated with the Epstein-Barr virus (EBV). Treatment-related myelodysplastic syndromes (tMDS) and second leukemias are extremely rare. Both autologous and allo-HCT carry increased risks for second solid malignancies (SSM). The cumulative incidence of SSM continues to increase in each of the largest studies with as much as 20 years of follow-up, likely related to the long latency of radiation-related SSM. Systematic, prospective monitoring, vigilant screening processes, and well-maintained survivorship clinics and databases are absolute necessities, and should be included in the infrastructure of individual transplant centers and networks, with mandatory periodic reporting of second malignancy incidences. Primary care and transplant physicians alike must be aware of the risk of second malignancies after allo-HCT. Most importantly, guidelines should be developed in regard to screening and prevention of second malignancies, so that physicians can provide state-of-the-art counsel and care for the benefit of our patients.

The blood microvasculature in T-cell lymphomas. A morphological, ultrastructural and immunohistochemical study

The microvasculature of lymph nodes of 55 cases of T-cell lymphoma was studied by light microscopy, immunohistochemistry and electron microscopy. A modified peroxidase-antiperoxidase (PAP) method was used for staining paraffin sections with lectin I of Ulex europaeus (UEA-I), which is a specific marker for vascular endothelial cells. The T-cell nature of each case was proven by immunohistochemistry, including immunoperoxidase staining of frozen sections with monoclonal T-cell antibodies. The cases were subclassified according to previously established criteria, but with the addition of a separate group showing a high content of clear cells. For the purpose of the present study, the small blood vessels were separated into two main variants, viz.: high endothelial venules (HEV) and all other types of vessels with flat endothelium (SVFE). The development of each of these variants and the extent of lymphocyte migration through the vascular wall were assessed semiquantitatively. The findings suggest that the blood microvasculature, as a whole, is similar in all types of T-cell lymphoma. There were distinct differences, however, in the development of the two main categories of small vessels between the various types. Chronic lymphocytic leukaemia of T-type (T-CLL) and Sézary's syndrome were poor in SVFE and rich in HEV, and there was considerable lymphocyte traffic through the latter. In contrast, T-immunoblastic and especially T-lymphoblastic lymphocyte traffic. The appearance of the microvasculature varied markedly in the various subtypes of "pleomorphic T-cell lymphoma". In the small cell subtype HEV predominated and SVFE represented only a small or moderate fraction of the microvasculature. As the size of the neoplastic lymphoid cells increased towards the medium-sized and large cell subtype, there was a decrease in the number of HEV and an increase in the number of SVFE accompanied by a decrease in lymphocyte migration. In T-cell lymphoma of the clear cell type the microvasculature showed features between those of T-CLL and the small cell subtype of pleomorphic T-cell lymphoma. Electron microscopy confirmed the light microscopic findings and revealed many similarities in vascular changes between "pleomorphic T-cell lymphomas" and lymphogranulomatosis X.