Reconstitution of Memory T -Cells after Allogeneic Stem Cell Transplantation in Patients with Post-Transplantation Cyclophosphamide As Tolerance Induction

Introduction.

Nowadays high-dose post-transplantation cyclophosphamide (CY) replace standard immunosuppression (IST). Thereby, the investigation of T-cells reconstitution after post-transplant-CY doesn't reach appropriate level, and probably it's very different from what we see after standard IST. We studied the reconstitution of memory T-cells on day of engraftment (WBC>1000 cells\us) after allogenic hematopoietic stem cell transplantation (allo-HSCT) with post-transplant-CY and standard immunosuppression therapy.

Patients and methods.

During 2 years, 29 patients with different hematological malignancies were included in this study. Median of age was 36 years (24-60 years). 16 patients were males, 13 - females. 22 received RIC, 7 - myeloablative regime. Match unrelated donor (MUD) was in 17 cases, "Mismatch" MUD - 2, Match related donor (MRD) - 9, "Mismatch"MRD - 1. 4 patients were in relapse or disease progression. CY as alternative IST was administrated to 6 patients. Standard immunosuppression consisted of CSA, MMF or MTX at standard dose. Peripheral blood samples were collected in EDTA-tubes at day of engraftment after allo-HSCT (Me= 20 day (14-35)). Isolation of mononuclear cells from human peripheral blood was made by standard protocol using Lympholyte®-M Cell Separation Media (Cedarlane Labs). The anti-CD4- APC-Cy7 antibody (Becton Dickinson, USA) and FSC/SSC were used for determine population of CD4+T-cells. Anti-CD45R0- FITC (Becton Dickinson, USA) antibody were used to determine memory T-cells as subpopulation of CD4⁺ T-cells. Due to cyto- and lymphopenia 1,000,000 events was analyzed.

Results.

Mann-Whitney U test was used to test for differences between memory T-cells (CD4⁺ CD45R0⁺) after post-transplant-CY alone and in a group with standard IST. The percent of memory T-cells in CD4+ cell population at day of engraftment after post-transplant CY alone was statistically higher (74,3% ± 5,1% ,p=0.048*) than in patients with standard immunosuppression (49,4%±6,7%).

Conclusion.

We may conclude that patients with post-transplant CY had a different "T cell reconstitution profile". Reported data show us that probably post-transplant CY spares memory T-cells in contrast with standard IST, and also probably that CY is more selectively immunosuppressor than "gold standard" (such as CSA, MMF and etc.) not only on effector T-cells population. Despite the fact that the analyzed group is small, obtained data is important and needs further investigation.