Comparison of the Distribution and Clonal Expansion Features of the T-Cell γδ Repertoire in Myelodysplastic Syndrome-RAEB and RAEB with Progression to AML

Myelodysplastic syndrome (MDS) is a heterogeneous group of clonal hematopoietic stem cell diseases. Approximately 30% of patients with MDS will develop acute myeloid leukemia (AML). Immune dysregulation may contribute to MDS initiation and progression. The altered expression and clonal expansion of the V beta repertoire were observed in patients with MDS. To further examine the characteristic features of gamma delta(+) T cells in MDS, we investigated the distribution pattern and clonal expansion capacity of the T-cell receptor (TCR) V gamma and V delta repertoire in patients with refractory anemia with excess of blasts (RAEB) and compared the difference between groups of patients with RAEB and RAEB-AML. Thirty-one patients with newly diagnosed MDS-RAEB were enrolled, and 9 of the 31 patients with RAEB developed AML (RAEB-AML). The TCR V gamma subfamily expression frequencies were similar in the RAEB and RAEB-AML patient groups. The number of the TCR V delta subfamilies expressed in the RAEB group was higher than that in the RAEB-AML group. In most cases, a significantly higher V delta 4 subfamily expression frequency (63.64%, 14/22) could be detected in the RAEB group, whereas only 11.11% (1/9) was found in the RAEB-AML group (p = 0.0079). At least one clonally expanded TCR V delta subfamily member was detected in all cases in both groups. V delta 3 was the most frequent clonally expanded T cell subfamily member found in the RAEB and RAEB-AML group, while the most frequent clonally expanded T cell subfamily member in the RAEB-AML group was V delta 8 (87.5%, 7/8), which was significantly higher than that in the RAEB group (42.86%, 9/21; p = 0.0307). In conclusion, the TCR V delta subfamily expression pattern exhibited a marked restriction in patients with RAEB-AML. The lower V delta 4 frequency and higher clonally expanded V delta 8 T cell alterations were the characteristic features found in RAEB-AML. These results provide new data regarding the immunodeficiency and immune reactive characteristics of patients with RAEB and RAEB-AML.