Antigen-recognition sites of micromanipulated T cells in patients with acquired aplastic anemia.
OBJECTIVE
Acquired aplastic anemia (AA) is a rare disorder characterized by pancytopenia and hypocellular bone marrow. Though experimental and clinical data suggest that AA represents a T cell-mediated disease, neither the immune response nor the nature of inciting antigen(s) have been characterized so far. The identification of a restricted T cell repertoire by PCR techniques in total lymphocyte populations supports an antigen-driven T cell response. In order to investigate the clonal composition, we analyzed the gene rearrangements of the T cell receptor (TCR) variable beta chain (Vbeta) at the single-cell level.


METHODS
CD3(+) T lymphocytes were micromanipulated from peripheral blood and bone marrow samples of 8 AA patients and healthy controls. Subsequently amplified VDJ gene segments of the TCRVbeta chain were analyzed for functional rearrangements. More than 500 functionally rearranged TCR loci were studied for Vbeta/Jbeta gene segment usage and molecular composition of the complementary-determining region 3 (CDR3).


RESULTS
In comparison to healthy controls, the Vbeta sequences confirmed a highly restricted T cell repertoire in AA patients at the single-cell level. Both in bone marrow and peripheral blood a predominance of Vbeta13 and Jbeta2S7 was observed. Furthermore, individual clonal T-cell expansion was identified in the majority of patients. However, deduced CDR3 amino acid sequences revealed a high variability without common motifs among the 8 patients.


CONCLUSIONS
Individual clonal T-cell expansion with high diversity of the antigen-binding sites among the analyzed patients argues for the predominance of private inciting epitopes in AA.
Piao
Wenji
W
Department of Hematology, Hemostaseology and Oncology, Hannover Medical School, Germany.
Grosse
Jens
J
Czwalinna
Andreas
A
Ivanyi
Philipp
P
Ganser
Arnold
A
Franzke
Anke
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D000741:Anemia, Aplastic / Q000188:drug therapy / Q000276:immunology*; D000961:Antilymphocyte Serum / Q000627:therapeutic use; D016572:Cyclosporine / Q000627:therapeutic use; D005260:Female; D015329:Gene Rearrangement, T-Lymphocyte; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013601:T-Lymphocytes / Q000276:immunology*
D000961:Antilymphocyte Serum; D007166:Immunosuppressive Agents; D016572:Cyclosporine