Many Faces of CD4-CD8-γδ+ T Cells in Peripheral Blood and Bone Marrow
Y-H Chen, L Peterson. Northwestern University Feinberg School of Medicine, Chicago, IL
Background: The TCR- γδ -positive T cells comprise a minor population (0.5-5%) of T cells in the peripheral blood in normal subjects. These cells are usually CD4- and CD8-. They play an important role in the immune response to infections, and may also have function in immune and tumor surveillance. T cell malignancies arising from this subpopulation are rare; hepatosplenic T cell lymphoma (HSTCL) and a subset of cutaneous T cell lymphomas are the diseases commonly known to feature a γδ T-cell phenotype. The expansions of this cell population in benign or malignant conditions are relatively less well recognized.
Design: In this study we compared clinical findings and morphologic diagnosis with flow cytometric (FC) results in a series of patients with expansion of CD4-CD8-γδ+ T-cells in the peripheral blood (PB) and/or bone marrow (BM). Patients with increase in this subpopulation of T cells and analyzed by FC between Jan. 2000 and Jun. 2009 were searched from the database of Northwestern Memorial Hospital. The corresponding clinical histories were also retrieved.
Results: A total of 76 cases (48 BM and 28 PB) from 63 patients were found. All patients showed CD4-CD8-γδ+ T cells >15% of total T cells. Among 63 patients, the expansion of this cell population most likely represents reaction to the underlying medical conditions in 44 patients, represents PB or BM involvement by cutaneous T-cell lymphomas in 6 cases, BM involvement by a peripheral T cell lymphoma that cannot be further classified in 5 cases, a rare variant of T-cell large granular lymphocyte (T-LGL) leukemia in 3 cases, HSTCL in 1 case and T-ALL in 1 case. No adequate information was available in 3 cases. The underlying medical conditions in patients with reactive proliferation of this subset of T cells include infection (HIV, hepatitis C, infectious mononucleosis) in 6 cases, organ or BM transplant in 5 cases, history of B or T cell lymphomas in 19 cases, AML or ALL in 6 cases, ITP in 2 cases, sarcoidosis in 1 case, and cyclic neutropenia in 1 case.
Conclusions: The expansion of CD4-CD8-γδ+ T cells in PB and/or BM range from reactive changes to aggressive T-cell malignancies. In particular, CD4-CD8-γδ+ T-LGL leukemia (3 cases in this series) is a relatively indolent disease. It may morphologically and phenotypically resemble the aggressive type of T-cell lymphoma, HSTCL. Recognizing the wide spectrum of conditions that may cause expansion of this unique subset of T cell population and correlation with clinical information and ancillary studies is important in making an accurate diagnosis.
Monday, March 22, 2010 2:45 PM
Platform Session: Section B, Monday Afternoon