No abstract

* Authors on the Steering Committee contributed equally to the oversight of the study, including study design and maintaining the quality of study conduct. CONTRIBUTORS Owen O'Connor, Barbara Pro, Tim Illidge and Lorenz Trumper formed the ECHELON-2 steering committee and contributed equally to the oversight of the study, including study design and maintaining the quality of study conduct.

Peripheral T cell lymphomas are a heterogeneous group of post-thymic, mature lymphoid malignancies, accounting for approximately 10-15% of all non-Hodgkin's lymphomas. A rare entity within this group is represented by hepatosplenic ␥␦ T cell lymphoma, which is characterized by primary extranodal disease with typical sinusoidal or sinusal infiltration of the liver and the spleen, respectively, by expression of the T cell receptor ␥␦ chain, and by a number of other frequent clinicopathological features including aggressive course of disease. In contrast to these common attributes some biologic characteristics such as expression of cytotoxic proteins and cytotoxic activity have been controversial. In this review, clinicopathological, immunophenotypical, molecular biological, cytogenetical and biological findings, and diagnostic and therapeutic difficulties in hepatosplenic ␥␦ T cell lymphoma are discussed. Leukemia (2000) 14, 991-997.

Insulin-dependent diabetes mellitus (IDDM) is a T-cell-mediated autoimmune disease whose onset is believed to be triggered by unknown environmental factors acting on a predisposing genetic background. Islet-infiltrating T (IIT) cells from two IDDM patients, who had died at the onset of the disease from brain swelling as a complication of ketoacidosis, were analysed. The results provided evidence for the involvement of a pancreatic islet cell membrane-bound superantigen as a diabetes aetiopathogenetic factor. There was a selective expansion of a T-cell receptor (TCR) variable segment of the beta-chain (V beta 7) in these IIT cells in association with unselected V alpha-chain segments; extensive junctional diversity of the TCR V beta 7 chains; and evidence of positive selection, after exposure to diabetic islet cell membrane preparations, of V beta 7+ T-cell clones among peripheral blood lymphocytes from non-diabetic individuals.