Biomolecular Characteristics of Specific Regulartory T Cells of Graft-Versus-Disease Based on T-Cell Receptor Analysis,

Abstract 4067

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an important therapetic option for a number of malignant and refractory haematological diseases. Graft versus host disease (GVHD) is the main complications following allo-HSCT. Recent data indicated that regulartory T (Treg) cells might participate in mediating GVHD and graft-versus-leukemia (GVL) effect after allo-HSCT. However, the distribution and clonality of T cell receptor (TCR) repertoire of specific Treg cells in GVHD remains unclear. To further characterize this feature, we analyzed the distribution and clonality of TCR repertoire of Treg cells at GVHD onset to further understand the biological characteristics of specific Treg cells subsets of GVHD.

The complementarity-determining region 3 (CDR3) sizes of TCR repertoire (TCR Vα, Vβ, Vδ and Vγ subfamilies) were analyzed in the Treg cells of recipients at GVHD onset, using RT-PCR and genescan technique. To determine the expression levels and expression pattern of TCR Vγ I-III subfamily genes, the expression levels and expression pattern of CD3 γ, δ, ε, ζ genes, and the expression levels of regulatory genes of Treg cells (FOXP3 and GATA-3 genes), we performed quantitative analysis by real-time PCR.

The frequency of TCR Vβ subfamilies of Treg cells at GVHD onset was significant lower than that in the Treg cells without GVHD. Oligoclonality were detected in TCR Vα 15, Vα 23, Vβ 14 and Vδ 3 subfamilies of the Treg cells from GVHD patients, and oligoclonality were detected in TCR Vα 4, Vα 21, Vβ 16 and Vβ 19 subfamilies of the Treg cells from patients without GVHD. The TCR Vγ I-III subfamilies expression levels in Treg cells were decreased significantly after allo-HSCT. The expression pattern of TCR Vγ subfamilies of Treg cells at GVHD onset was TCR Vγ III>TCR Vγ I>TCR Vγ II, and different with the expression pattern of Treg cells without GVHD (TCR Vγ I>TCR Vγ II>TCR Vγ III). The expression pattern of CD3 γ, δ, ε, ζ genes of Treg cells at GVHD onset was also changed, and GVHD might mainly influence the expression levels of CD3 δ and CD3 ε genes of Treg cells. The expression levels of GATA-3 gene had a positive correlation with the expression levels of FOXP3 gene in Treg cells with GVHD. The expression levels of GATA-3 gene in Treg cells at GVHD onset were significant higher than that in the Treg cells without GVHD, but the expression levels of FOXP3 gene in Treg cells at GVHD onset were significant lower than that in the Treg cells without GVHD.

In conclusion, oligoclonality of TCR Vα 15, Vα 23, Vβ 14 and Vδ 3 subfamilies of Treg cells might related with GVHD. The expression pattern of high TCR Vγ III gene expression and low TCR Vγ II gene expression in Treg cells might correlate with GVHD. GVHD might mainly influence the expression levels of CD3 δ and CD3 ε genes in TCR signal transduction of Treg cells. The high expression levels of GATA-3 gene in Treg cells might play a role in mediating GVHD, and GATA-3 could be a novel treatment target of GVHD immunotherapy.