Donor lymphocytes may acquire cytolytic specificity to donor's engrafted hematopoietic cells after a hematopoietic stem cell allograft resulting in marrow failure.

BACKGROUND

Secondary rejection sometimes occurs after engraftment of allogeneic hematopoietic stem cell transplantation (allo-HSCT), which results in marrow failure. To clear possible reasons for BM failure, we observed a patient with acute myeloblastic leukemia who died of hematopoietic failure one year after apparently successful allo-HSCT.

METHODS

The patient was a 44 year old male. Allo-HSCT was successful after 40 days, and 100% of marrow cells were of donor's origin. Graft-versus-host disease (GVHD) began at the 60th day with involvement of multiple organs. He died of marrow failure on the 360th day after allo-HSCT.

RESULTS

We identified the origin of the patient's lymphocytes by a donor's specific HLA locus, and a dominant T-cell clone by spectratyping of the TCRVB subfamily on T-cells. The patient's dominant CD8+ cells were separated by magnetic beads and incubated with donor's cells or patient's leukemic cells to evaluate their cytolytic specificity. TCRalpha and TCRbeta cDNAs were cloned from the dominant CD8+ T-cells, transfected into Jurkat cells, and characterized the cytolytic specificity of the transfected Jurkat cells. In the period of 60 to 120th day after allo-HSCT, blood CD3+CD8+ cytotoxic T lymphocytes (CTLs) gradually increased and fluctuated in the range of 60 to 90%, CD3+CD4+ cells fluctuated in the range of 5 to 18%, and CD4+CD25+ cells accounted for between 3 to 13%. Spectratyping of the 24 TCRVbeta subfamilies in blood lymphocytes demonstrated a dominant TCRVbeta13.1 clone with HLA-A*0201 of donor origin. The dominant CD8+ cells separated by magnetic beads showed cytolytic specificity to donor's blood mononuclear cells (BMCs), but not to patient's fibroblasts. Jurkat cells containing the cDNAs of TCRalpha and TCRbeta chains cloned from the dominant CD8+ cell clone had cytolytic activity against donor's BMCs, patient's leukemic cells, and BMCs from an unrelated subject accounting for 43%, 15%, and 0.42%, respectively. The dominant lymphocyte clone of donor's origin with CD3+CD8+ TCRVbeta13.1 markers in the patient may have been determinant in the hematopoiesis failure.

CONCLUSIONS

Donor's lymphocytes changed in the recipient, acquiring the cytolytic specificity to donor's hematopoietic cells and presumably leading to marrow failure.