Dominant T-Cell Clonal Expansion Associated with Acute Graft-Versus-Host Disease after Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Patients.

Allogeneic hematopoietic stem cell transplantation (AHSCT) provides a valuable therapy for a variety of malignancies, solid tumors, hematological disorders and autoimmune diseases. One of the major complications in recipients after transplantation is graft-versus-host disease (GvHD), which can cause delayed T-cell reconstitution and therefore increase the risk of infection and mortality. It has been suggested that T cells play an important role in the development of GvHD. Several previous studies have identified T-cell clones associated with acute GvHD in adult patients. However, T-cell clonal expansion in the early stage of post-transplantation might also be caused by T-cells which are unrelated to acute GvHD. In this study, we used TCRβ CDR3 size spectratyping to detect T-cell clonal expansion among the polyclonal complexities of peripheral blood. We examined the TCRβ repertoire distribution at the onset of acute GvHD in 10 pediatric patients. We then compared that result with the TCRβ pattern at the same post-AHSCT stage in another 10 pediatric patients without acute GvHD.

Method: An RT-PCR assay for Vβ CDR3 size distribution was performed. Each fluorescent PCR product was detected by an automated 310 DNA sequencer. The data were analyzed by GeneScan software.

Results and Discussion: As expected, the TCRβ repertoire distribution was much skewed for all patients in both groups, because the immune suppression occurred at early stage of post-AHSCT. There were about 4–8 T-cell clones expanded in each patient for both groups. The TCRβ subfamilies among those clones varied significantly from patient to patient. However, Vβ2, Vβ9, Vβ13 and Vβ20 were commonly found in both groups, indicating in these cases that clonal expansion was not related to the occurrence of acute GvHD. Notably, TCR Vβ16 was found in 9 of 18 samples from 7 of 10 patients with acute GvHD. This TCR subfamily was not dominant in the patients without acute GvHD. This finding strongly suggests that the T-cell clone carrying TCR Vβ16 subfamily might be associated with acute GvHD in pediatric patients. The characterization of this T-cell clone is under study.