Analysis Of Peripheral Blood γδT Cell Subsets And Functions In Patients With Pure Red Cell Aplastic Anemia

Objectives Pure red cell aplastic anemia (PRCA) is a group of heterogeneneous disorders characterized by erythropoiesis failure or disorder in bone marrow. PRCA has been associated with thymoma, large granular lymphocytic leukemia, and also some autoimmune diseases, such as systemic lupus erythmatosis. T cell subsets from the patients with PRCA often show some abnormalities in quantum, and the effect to suppress erythropoiesis has been well documented in vitro culture. Recently, gene rearrangements of TCR of PRCA have been studied by Southern blot analysis, and clonality of T cell has been found. The anemia in patients with PRCA generally responds to immunosuppressive drugs, including corticosteroids, cyclosporine, and cyclophosphamide. So it suggested that activated T cell may play a key role in the pathogenesis of PRCA. This study is to explore the abnormalities both in quantum and function of γδT cell subsets and the effect of immunosuppressive therapy in the PRCA patients. Material and Methods 11 patients were diagnosed as PRCA in WestChina Hospital of Sichuan University from September, 2003 to April, 2004, and were treated with cyclosporine A; The patients were classified into two groups according to their responses to therapy. Responsive group included whose hemoglobin level increased to normal or improved 30g/L after treatment. 23 healthy adults were analyzed as normal controls. The three-color flowcytometry technique was used for lymphocytes subsets and y5 T cells analyses, and T cells cultured in vitro were set at 106 cell/ml in RPMI1640 medium supplemented with 10% FCS , lOug/ml phytohemagglutinin (PHA), 50U/ml recombinant human interleukin-2 (rIL-2) for two weeks. The y8T cells were isolated with the TCRyS Microbead Kit from T cell cultured cells, then the patients' yST cells were incubated with normal bone marrow mononuclear cells in RPMI1640 medium at 37 □ in a humidified 5% CO2 atmosphere for clone assays. CFU-E and CFU-GM clones scored were on day 7, on day 14 for BFU-E assay. Results The percentage of the cells bearing the marker CD3 and CD8 was significantly increased in the patients comparing with controls (PO.05), and CD4+/CD8+ ratio was reversed. T cells with y6-TCR were overrepresented in those patients (P<0.05 ) . While after treatment, CD3+, CD8+ cells and y8T cells were decreased in patients of responsive group. Number of y8T cells of irresponsive group was still similar to that of group before treatment. Moreover, y5T cells isolated from PRCA patients played an inhibiting role to CFU-E and BFU-E but not CFU-E in a dose-dependent manner in vitro culture.Conclusion This study has suggested that : First, y8T cells might play a key role in pathogenesis of PRCA; Second, a significant improvement ofanemia symptoms had shown in the patients with PRCA and the percentage of y8T cells recoverd to normal range after cyclosporine A treatment; And finally, y8T cells could inhibit CFU-E and BFU-E but not CFU-E clone growth in a dose-dependent manner.