Characterization of Peripheral Immune Cells in Kidney Transplantation Recipients under Different Immunosuppressive Treatments

Yunze Tai¹Nanjing Li²Jiwen Fan¹Haohan Zhang³Honghui Long⁴Lin Yan¹Weihua Feng¹Junlong Zhang¹Bei Cai¹Yao Luo^1*Yu Fan^3*Yi Li^1*

• ¹Department of Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China
• ²Department of Radiotherapy, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China
• ³Department of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China
• ⁴West China Hospital, Sichuan University, Chengdu, Sichuan Province, China

Background: A comprehensive peripheral immune cell characterization including novel immunosuppressive subsets myeloid-derived suppressive cells (MDSCs) in kidney transplant recipients (KTRs) under different immunosuppressive treatments can help: 1) Immunosuppression situation and allograft acceptance assessment; 2) Infection and rejection emergence indication; 3) Beneficial immunosuppressive regimens' selection.Methods: 26 KTRs with an average transplant duration of 360 days and 13 healthy controls were enrolled in this study. 11KTRs were included in the SRL-based therapy group and the other 15 in the TAC-based therapy group. Flow cytometry was used to detect the percentages and absolute numbers of MDSCs, T cell populations, HLA-DR + monocytes, neutrophil CD64 index, and cytokines in peripheral blood.In KTRs, the expression of G-MDSCs and M-MDSCs was significantly higher than the HCs, while the expression of HLA-DR + monocytes, CD38 + /CD28 + activated T cells, CD4 + naï ve T cells, CD4 + effector memory T cells, and central memory T cells were significantly lower. The use of mTOR inhibitors in KTRs induced changes in the distribution of activated and naï ve-memory T cell subsets and decreased proinflammatory cytokines.In KTRs, G-MDSCs and M-MDSCs accumulated while functionally activated, naï vememory T cell populations and HLA-DR + monocytes markedly decreased one year after transplantation. Additionally, the number of MDSCs and T cell subsets following transplantation is likely regulated by mTOR inhibitors. (2161612), anti-CD11b-PC7 (1335874), anti-CD33-FITC (1285601), anti-CD16-PE (1307994), anti-CD15-APC (1180500) (all from BD Biosciences). Antibodies were used at a dilution of 1:20 according to the manufacturer's instructions. G-MDSCs were defined as CD11b + CD33 + CD14 - CD15 + HLA-DR -CD16 -and M-MDSCs were defined as CD11b + CD33 + CD14 + CD15 -HLA-DR -. The detailed gating strategy is shown in Supplementary Figure 1The following mAb panels (all from Beckman Coulter) were used for regulatory T cells (Tregs):