OBJECTIVETo study the molecular characteristics of CDR3 repertoires of T cell receptor beta chain variable region (TCRBV) of T lymphocytic clones in leukemia recipients after allogeneic hematopoietic stem cell transplantation ( allo-HSCT).

METHODSRT-PCR was used to amplify 24 subfamily genes of TCRBV from peripheral blood (PB) lymphocytes in twenty-four leukemia patients underwent three kinds of allo-HSCT and in five normal donors as control. The PCR products were further analyzed by genescan to evaluate the clonality of BV subfamily and characteristics of CDR3 and calculate usage rate of BV subfamily. The monoclonal bands which associated with GVHD and CMV infection were obtained by denaturation polyacrylamide gel electrophoresis and sequenced. Comparison of the sequences of TCRBV CDR3 with other CDR3 sequences which associated with GVHD or CMV infection was reported.

RESULTS2 approximately 19 months after transplantation, there were 6 approximately 14 BV subfamilies expressed and the polyclonal expression reached 33% in nine patients underwent haploidentical bone marrow transplantation(HI-BMT). In five patients underwent matched unrelated peripheral blood stem cell transplantation ( MU-PBSCT), there were 10 approximately 15 BV subfamilies expressed of which 45% were poly-clones. In 10 patients underwent matched sibling bone marrow transplantation(MS-BMT), 10 approximately 16 BV subfamilies were expressed and more than 48% of them were poly-clones. Monoclones and oligo-clones existed in 24 BV subfamilies but no common one monoclone BV subfamilies was found. Immune reconstitution in patients underwent HI-BMT was later than that in other two groups. In 2 patients TCRBV was detected in 2m and 3m after allo-HSCT and found that there was a tendency of increasing usage of BV subfamilies and increasing expression of CDR3 polymorphism. Twenty three TCRBV CDR3 molecules associated with GVHD and CMV infection were compared each other by bioinformatics and found that different cases of the same BV subfamilies may share similarity in amino acid motif, while in different BV subfamilies none appeared to share the same amino acid motif.

CONCLUSIONIn 1.5 years after allo-HSCT, the usage of TCRBV subfamilies still restricted. Immune reconstitution in patients underwent HI-BMT was later than that in other two groups. TCRBV CDR3 molecules associated with GVHD and CMV infection showed that different cases of the same BV subfamilies may share similarity in amino acid motif, while in different BV subfamilies none of clones appeared to share the same amino acid motif.