Download PDF version
Cellular Therapy and Transplantation (CTT)
Volume 6, Number 3
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is one of the most effective therapy for patients with hematologic malignancies. Its success depends on many factors such as patient age, comorbidities, conditioning regimen etc. In most cases, however, the efficiency of immune reconstitution appears to be the crucial factor determining allo-HSCT success. Bone marrow resident CD8+ T cells comprise the main pool of adaptive immunity against pathogens and tumors. Here we describe an impact of a high-dose post-transplant сyclophosphamide (PTCy) upon reconstitution of bone marrow (BM) resident CD8+ T cells after allo-HSCT. The aim of this study was to evaluate real impact of high-dose PTCy on bone marrow pool of CD8+ T memory cells in allo-HSCT patients.
Patients and methods
Bone marrow (BM) samples were collected on day +30, +60 and +90 after allo-HSCT in EDTA-tubes. The group consisted of 19 patients (9 males and 10 females) with a median age of 36 years (20-60 years old) who underwent allo-HSCT between September 2016 and February 2017. All the patients had hematological malignancy (ALL, 3; AML, 13; LPD, 3). Sixteen patients were in complete remission, and 3 patients were transplanted in progressive disease. Myeloablative conditioning regimen (MAC) was used for 7 patients and reducedintensity conditioning (RIC), in 12 patients. The GVHD prophylaxis included on classical immunosuppressive therapy (n=12), or a post-transplant treatment based on high-dose cyclophosphamide (PTCy) on day +3, +4 (n=7), as follows: CsA+MMF+MTX+ATG (n=11), PTCy+ATG (n=2), CsA+MMF+PTCy+ATG (n=5), CsA+MTX (n=1). Flow cytometry analysis was performed by means of BD FACS Canto II machine (Becton Dickin-son, USA). 7-AAD was used to exclude dead cells from analysis. The anti-CD8-APC-Cy7, anti-CCR7-PE-Cy7, anti-CD28-PE, anti-CD45R0-FITC antibodies (Becton Dickinson, USA) were used to define T memory subsets: T naive and T stem cell memory (Tnv+Tscm) were identified as CD8+CD45R0-CCR7+CD28+; T central memory cells (Tcm), as CD8+CD45R0+CCR7+CD28+; T transitional memory cells (Ttm), as CD8+CD45R0+CCR7-CD28+; T effector memory cells (Tem), as CD8+CD45R0+CCR7-CD28-; T terminal effector cells (Tte), as CD8+CD45R0-CCR7-CD28-. Mann-Whitney U test was used for non-parametric data analysis. A p value less than 0.05 was considered to be statistically significant. The entire data analysis was conducted with SPSS ver. 23. (IBM, Chicago, Ill., USA).
In these subgroups of the patients, we show the lower numbers of Tnv+Tscm CD8+ cells in BM within 100 days of follow up period after allo-HSCT in patients who were treated with PTCy com-pare to the group of patients with classical immunosuppressive regimen (p<0,05). Detailed data are presented in Table 1.
The use of PTCy for immunosuppressive regimen mostly affects bone marrow CD8+ Tnv+Tscm cells. These populations demonstrate antigen-independent proliferation in BM and represent the main source of CD8+ T cells ensuring adoptive immunity. Hypothetically reduced Tnv+Tscm CD8+ cells in BM after PTCy can play a key role not only in preventing GVHD due to the lack of allore-active T-cell pool, but they can also lead to immune insuffciency and post-transplant complications such as malignancy relapses and infections. These issues need to be clarified in further research.
No relevant conflicts of interest to declare.
Bone marrow resident T cells, T memory cells, immune reconstitution, stem cell transplantation, post-transplant high dose cyclophosphamide.