Discussion
In this study we used mass cytometry to investigate the effect of the application of MSC therapy at week 6 and 7 after kidney transplantation with concomitant tacrolimus withdrawal on a background of alemtuzumab and mTOR inhibitor. In previous work we described successful tacrolimus withdrawal after MSC infusion [MSCs can affect many types of immune cells including dendritic cells, monocytes, macrophages, B cells, T cells (Treg/Th1/Th2 and Th17 helper cells), NK cells and NKT cells, ILCs, myeloid-derived suppressor cells, neutrophils, and mast cells through a combination of direct cell-cell contact and soluble factors (reviewed by Weiss et al. and Jiang et al. [In the current study alemtuzumab was used as induction therapy, resulting in profound depletion of circulating lymphocytes. As expected, we could confirm that repopulation after induction therapy is still ongoing at 52 weeks, as the number of CD4In the TRITON trial, MSCs were administered to facilitate safe tacrolimus withdrawal. Although the MSC patients with tacrolimus withdrawal developed more dnDSA then the control group, their kidney function was not inferior and dnDSA development did not lead to more rejection episodes [Tacrolimus inhibits the calcineurin pathway preventing dephosphorylation of NFAT (nuclear factor of activated T lymphocytes) and its translocation to the nucleus. This blocks the activation of the IL-2 gene, involved in T cell activation and as a result the initiation of the immune response [The analysis performed in this study was an unbiased discovery analysis using a large number of immune cell markers. Therefore, many phenotypically different clusters could be identified, and as a result a high number of comparisons were made. In this study we corrected with Bonferroni for the three comparisons made within one cluster. Correcting for false positives within the whole study, with the current statistical options, would result in the need for extremely low In conclusion, this study provides a comprehensive description of the PBMC subsets in kidney transplantation patients after MSC therapy and subsequent tacrolimus withdrawal. Our results point towards an active involvement of CD4We thank the research technicians from the Transplant Immunology lab for technical assistance with PBMC biobanking and absolute cell counts.