Association with the presence of naive T cells in chronic myeloid leukemia patients after allogeneic human stem cell transplantation and the lower incidence of chronic graft-versus host disease and relapse.

Introduction: Allotransplantation in chronic myeloid leukemia (CML) patients offers long-lasting remissions, which largely depend on immunologic surveillance of alloreactivity. Alloreactivity in CML patients has a durable potential. However a large proportion of relapsing patients, who have to undergo donor lymphocyte treatment is still abundant.

Methods: We studied a group of 31 CML patients post allogeneic transplantation for their level of T-cell receptor excision circles (TREC) and proportion of naive and memory/effector T cells in the peripheral blood (PB). TREC numbers were determined by quantitative PCR (qPCR) and T-cell subsets CD4(+)CD27(+)CD45RO(-), CD4(+)CD27(-)CD24RO(+), CD4(+)CCR7(+), and CD4(+)CCR7(-) by flow cytometry. Patients were analyzed for posttransplant chimerism, type of bcr-abl transcripts, and number of TREC in association with the presence of chronic graft-versus-host disease (cGVHD) and relapse. CML patients with TREC+ in PB had a higher proportion of CD4(+)CD27(+)CD45RO(-) cells (3.54 vs 2.45%; P = .105) and CD4(+)CCR7(+) cells (4.85 vs 2.67%; P = .007), and a lower proportion of CD4(+)CD27(-)CD45RO(+) cells (5.55 vs 9.09%; P = .037). The incidence of cGvHD was reduced among TREC+ CML patients (3/14 vs 11/17; P = .006).

Results: The 5 out of 31 CML patients who relapsed were characterized by the presence of b2a2, b3/a2 or both type of transcripts, a lack of TREC in the blood, and a lower proportion of naïve and effector/memory T cells. No association was observed between any of HLA specificities, type of bcr-abl transcripts and incidence of relapse.

Conclusion: The presence of TREC is affected by chronic GvHD; TREC negativity may constitute a risk of mixed chimerism and relapse.