Recent Thymic Output Function And TCR Vβ Repertoire Usage In Patients With Chronic Myelogenous Leukemia

Objective: To investigate the thymic recent output function (content of TRECs) and the gene expression of TCR Vβ subfamily T cells and clonality in patients with chronic myelogenous leukemia(CML). This study is expected to provide some basic data for research on clinical specific immune therapeusis.Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from 42 heparinized peripheral blood samples obtained from 38 patients. Some of PBMCs were used to separate CD4~+ and CD8~+ cells by using the MACS magnetic bead separation system. Quantitative detection of T-cell receptor excision DNA circles (TRECs) in DNA of PBMCs, CD4~+ and CD8~+ cells were preformed by real-time PCR analysis. And the TREC-number was related to the number of T-cells by determination of the number of CD3-positive cells. The gene expression and cloanlity analysis of TCR Vβ repertoire were detected by RT-PCR and genescan technique in PBMCs, CD4~+ and CD8~+ cells. 14 normal individuals served as controls.Results: There were dramatic reduction of TREC levels in PBMCs, CD3~+, CD4~+ and CD8~+ cells in patients with CML-CP compared with normal individuals. Whereas the TREC levels in CD3~+ cells from patients with CML who achieved complete remission or stayed at 6 months after allo-BMT were higher than CML-CP, and lower than normal individuals, although these were not statistically significant. The TRECs levels in different sex of normal individuals and patients with CML-CP were differ. Female normal individuals had significantly higher TRECs level in CD8~+ cells than male. While in patients with CML-CP this difference existed in CD4~+ cells. There were not statistically significant difference in other groups. All patients with CML only expressed some of Vβ subfamilies. On an average, they expressed averagely 5.52 Vβ subfamilies in PBMCs, 11.58 Vβ subfamilies in CD4~+ cells and 12.37 Vβ subfamilies in CD8~+ cells. Vβ13 was expressed most frequently. The expression of the number of Vβ subfamilies decreased significantly early stage after chemotherapy and gradually recoveried when the patients achieved complete remission. Genescan analysis showed that clonal expanded T cells in PBMCs, CD4~+ and CD8~+ cells could be identified in 70.4%, 73.7% and 89.5% patients with CML-CP respectively. In PBMCs and CD4~+ T cells, the clonal expanded T cells were found in 16 and 14 Vβ subfamilies respectively. The clonal expanded of Vβ 21 subfamily was identified most frequently. While in CD8~+ cells, clonal expanded Tcells could be detected in 20 Vp subfamilies. The clonal expanded of subfamily was identified most frequently. We also found that the expression of TCR 24 Vp subfamilies and clonal expanded Vp subfamilies were positive correlation to the contents of TRECs.Conclusions: It is the first report to describe the condition of thymic recent output function and peripheral T cells immune function in patients with CML. The clonal expanded T cells in patients were related to specific function of anti-CML. The main reason that these clonal expanded T cells were unable to anti-CML may relate to remarkble reduction of thymic recent output function in CML.