[Molecular characteristics of T-cell receptor of clonal expansion of T lymphocytes in leukemia patients after haploidentical bone marrow transplantation].

BACKGROUND & OBJECTIVE: Previous clinical and experimental results indicate that T-cell immune reconstitution is slow after hematopoietic stem cell transplantation. Immune reconstitution after haploidentical bone marrow transplantation (BMT) is closely related to clinical events. This study was to analyze the repertoire of T-cell receptor beta chain variable region (TCRBV) and the molecular characteristics of T-cell clones during immune reconstitution in leukemia patients after haploidentical BMT.

METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) was used to amplify 24 genes of TCRBV subfamily from peripheral blood lymphocytes of 9 leukemia patients after haploidentical BMT, and 5 healthy donors as control. The PCR products were analyzed by GeneScan to evaluate the clonality of BV subfamily, characteristics of complementarity determining region 3 (CDR3), and usage rate of BV subfamily. Graft-versus-host disease (GVHD)-related monoclonal bands were sequenced.

RESULTS: During 10-19 months after haploidentical BMT, the usage of TCRBV subfamily was still restricted. Deletion of some BV subfamily members was detected, while others expanded in monoclonal or oligoclonal. For 4 patients with stable disease, the expression of 9-14 BV subfamily members was detected, and more than 50% of them were polyclones. For other 5 patients with GVHD or cytomegalovirus (CMV)-pp65 infection, the usage of TCRBV decreased obviously(P<0.05), the expression of CDR3 were monoclonal or oligoclonal, only 30% were polyclonal. No common monoclonal BV subfamily members were detected. After treatment, the usage of BV subfamily and CDR3 polymorphism were increased in 2 patients. By analyzing the sequences associated with GVHD, none of the clones appeared to share any similarity in amino acid motif.

CONCLUSIONS: In 10-19 months after haploidentical BMT, the usage of TCRBV subfamily members is still restricted. In stable condition, there are 9-14 BV subfamily members expressed and dominated by polyclones. In active condition, the expression of BV subfamily members is decreased and dominated by monoclones or oligoclones. A group of CDR3 molecules related to GVHD show no common amino acid motif to be shared.