Emerging role of γδ T-cells in health and disease

The majority of T lymphocytes in the peripheral blood bear the αβ type of T-cell receptor (TCR) and less than 5% of circulating T lymphocytes bear the γδ type of TCR. The αβ and γδ T-cells contribute differently to the host immune defense. The immunologic function of γδ T-cell in humans is gradually unraveling. Pathologic studies have shown a relatively high proportion of γδ T-cells in the gastrointestinal mucosa, skin, and splenic red pulp where they appear to have an important immunologic function against pathogens attempting to enter body through the mucosal surfaces and possibly the skin. More data are emerging about the role of γδ T-cells in the course of infectious diseases and in the pathogenesis of autoimmunity. The possible role of these cells in immunologic surveillance against cancer has been inferred from their preferential expansion in certain malignancies. In parallel to the low frequency of these cells in normal lymphocytes, lymphomas bearing γδ type of T-cell receptors on cell surface are rare. These include hepatosplenic and non-hepatosplenic (including those involving the skin and those involving nasal cavity and upper aero digestive tract) and the rare non-B-cell cases of lymphomas seen in the immunosuppressed organ transplant patients. The limited available clinical data about γδ T-cell lymphomas suggest that these lymphomas tend to have an aggressive course particularly the hepatosplenic form with poor response to multi-agent chemotherapy and short median survival.