Exploration Of T Cell Subsets And Their Receptor Remodeling After Single Unrelated Cord Blood Transplantation

Objective Unrelated cord blood transplantation?UCBT?has a lower incidence of graft versus host disease?GVHD?^[1,2]and a unique anti-leukemia effect^[3,4].However,UCBT is also thought to be associated with delayed engraftment,poor T cell reconstitution,and the resulting increased risk of infection^[5-7].T cells are effector cells such as post-transplant infection,graft anti-leukemia,and GVHD.The rapid reconstruction of T cells after transplantation is the key to the success of transplantation.This study aimed to to explore the reconstruction of T cells and their receptors.Methods UCBT patients who underwent non-T-myeloablative conditioning were selected for T cell reconstitution monitoring.This experiment was conducted in two parts.Part I:Flow cytometry was used to monitor the reconstitution of T cells(CD3⁺,CD3⁺CD4⁺,CD3⁺CD8⁺and CD4⁺CD25⁺CD127^low)1 year after UCBT.The time points were set at 1,3,6,9 and 12 months after transplantation.At the same time,10 healthy subjects were included as normal controls.The second part,high-throughput sequencing?NGS?technology was used to monitor the diversity of TCR pools of 3 adult CB recipients.The time point was set at 3,6,9,and 12 months after UCBT,and one healthy adult was selected as a control.Results This experiment revealed the characteristics of T cell reconstruction in the treatment of acute leukemia with a single UCBT removed by non-T cells,and explored the post-transplant TCR reconstruction in this transplantation model for the first time.The experimental results are as follows:Part ?:Reconstruction of T lymphocytes and their subgroups after UCBT?1?Changes in T lymphocytes and their subpopulations after UCBT:The proportion and absolute number of T cells returned to normal in the third month after UCBT.Furthermore,the proportion and absolute number of CD8⁺T cells returned to the normal3 months after transplantation,while the proportion and absolute number of CD4⁺T cells returned to normal 6 months after transplantation.The proportion and absolute number of CD8⁺T cells after UCBT recovered faster than the proportion and absolute number of CD4⁺T cells.The absolute numbers of T cells and CD8⁺T cells were higher than the normal reference values 3 to 12 months after transplantation.?2?Changes in Treg lymphocytes after UCBT:The proportion and absolute value of Treg cells after UCBT were slower to rebuild,and did not return to the normal until 12months after transplantation.?3?The effect of age on T lymphocytes and their subgroups:The younger group?<18Y?Treg cells recovered faster than the older group??18Y?,whereas the T lymphocytes of the younger group showed a slower recovery trend than the adult group.And there was no significant difference in the recovery of CD8⁺T cells and CD4⁺T cells between the two groups after transplantation.Part ?:TCR diversity reconstruction:The recovery of CD4⁺TCR diversity was significantly faster than the CD8⁺TCR diversity.The diversity of CD4⁺TCR reached normal value from 3 to 9 months after transplantation,while CD8⁺TCR diversity recovered slowly and did not reach normal 12 months after transplantation.And both of CD4⁺TCR and CD8⁺TCR had CDR3 gene dominant expression.Conclusion 1.T-cells-repleted single UCBT reached normal T lymphocytes at 3 months after transplantation,and CD8⁺T lymphocytes recovered faster than CD4⁺T lymphocytes,reaching normal at 3 months and 6 months after transplantation respectively;2.the absolute number and proportion of Treg cells were low within one year after transplantation.Besides,age less than 18 years was conducive to the recovery of Treg cells.3.The recovery of CD4⁺TCR diversity was significantly faster than that of CD8⁺TCR diversity.The CD4⁺TCR diversity began to reach the normal value range3 to 9 months after transplantation,while CD8⁺TCR diversity did not reach the normal reference value even after one year of transplantation.