The thymic-dependent pathway that involves generation of new naive T cells from donor-derived precursor cells accounts for the more durable reconstitution of the T-cell compartment and generates a more diverse TCR repertoire. Thymic function and production of recent thymic emigrants (RTEs) may be directly evaluated through the quantification, by real-time polymerase chain reaction (PCR), of the T-cell receptor excision circles (TRECs). Following hematopoietic stem cell transplant (HSCT), there is a prolonged period of profound immune deficiency, which continues for years after HSCT. The factors that inhibit thymic function may include age, graft-versus-host disease (GVHD), and direct thymic damage from chemoradiotherapy. GVHD after HSCT also leads to thymic insufficiency, possibly by direct attack on the thymic stroma by allogeneic effector cells. The aim of our study is to analysis T cell receptor excision circles (TRECs) in patients with GVHD after allogeneic stem cell transplantation. We used real-time polymerase chain reaction (PCR) to quantify SjTRECs in 12 patients with GVHD(9 males, 3 females; median age 32 years old), who underwent HLA-matching sibling BMT and/or peripheral blood stem cell transplantation (PBSCT) at our department. Quantitative detection of sjTRECs in DNA of peripheral blood mononuclear cells from 13 normal individualals. The median value of sjTRECs copies P1 000 PBMCs was 4.37±3.64 in normal indiviuals. However, the decreased levels of TRECs were most profound in the group of patients with active chronic GVHD at the time of study. it was 0.26±0.22 copies P1 000 PBMCs in 12 patients with GVHD (P < 0. 00007). We conclude that measurement of sjTREC may provide an important tool for predicting thymus-dependent T-cell reconstitution in GVHD patients after transplantation.

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