Analysis of T Cell Cloanlity of Ph+ Acute Lymphoblastic Leukemia with Chronic Gvhd in Continuous Remission after Allogeneic Hematopoietic Stem Cell Transplantation

Chronic graft-versus-host disease (cGVHD) is one of the major complications following allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, recent study suggested that the presence of cGVHD might reduce the risk of relapse in Ph+ acute lymphoblastic leukemia (ALL) after allo-HSCT. GVHD is mediated by proliferation of special T-cell clones, we analyzed the T cell receptor (TCR) Vβ repertoire and cloanlity in Ph+ ALL patients undergone cGVHD after allo-HSCT in order to find the special T-cell clones associated with continuous remission.

Allogeneic transplantations were performed in the first complete remission (CR) (6 ALL^P190+ patients). The numbers of BCR-ABL copies in peripheral blood samples were assessed with the real-time quantitative RT-PCR (RQ-PCR) test at diagnosis, and every month after HSCT. The quantity of BCR-ABL transcript was normalized for normal ABL expression and the result was expressed as the ratio of BCR-ABL copies to ABL copies. With monitoring BCR-ABL copies of 6 BCR-ABL^P190+ ALL patients after HSCT (the mean ratio of BCR-ABL^P190/ABL at diagnose was 0.41 ± 0.39%), we found that 4 patients with extensive cutancous cGVHD had no evidence of leukemia recurrence, and the BCRABL transcripts of patients with cGVHD were remaining 0 copy, while 2 patients without cGVHD relapsed (the mean ratio of BCR-ABL^P190/ABL was 7.56 ± 2.49%) and even dead within six months of HSCT.

The expression and cloanlity analysis of TCR Vβ repertoire was detected in peripheral blood samples from patients with cGVHD by RT-PCR and genescan technique. TCR Vβ repertoires with polyclonal pattern were identified in normal controls and donor groups. However, the skew expression pattern of TCR Vβ repertoire could be detected in patients with cGVHD even more than 1 year after allo-HSCT. Among the 24 Vβ subfamilies, there were only 11~17 Vβ subfamilies expressed in cGVHD patients. Oligoclonal or monoclonal expanded T cells were identified in TCR Vβ 1, 2, 3, 7, 8, 12, 14, 16~20, 22 and 23 subfamilies in 4 ALL patients (BCR-ABL^P190 remission) with cGVHD. As a contrast, oligoclonal or monoclonal expanded T cells were identified in TCR Vβ 2, 7, 8, 14, 17, 20, and 22 subfamilies in 2 chronic myeloid leukemia patients (BCR-ABL^P210 remission) with cGVHD.

In conclusion, the predominant usage and clonal expansion of TCR Vβ subfamily T cells could be found in Ph+ ALL patients with cGVHD and these groups of specific T-cell clones (Vβ 1, 3, 12, 16, 18, 19 and 23) were potentially associated with cGVHD in ALL and might be responsible for maintaining CR in Ph+ ALL patients after allo-HSCT. Research Funding.