Full length articleThe advantage of Sirolimus in amplifying regulatory B cells and regulatory T cells in liver transplant patients
Graphical abstract
Introduction
Sirolimus, a member of the mammalian target of Rapamycin family, was originally investigated as an antibiotic (Ochiai et al., 1993). With further study of Sirolimus, its immunosuppressive function has been gradually recognized. However, the immunosuppression mechanism has been only partially revealed (Kim and Guan, 2015; Moes et al., 2015; Waldner et al., 2016). We found that some intractable steroid-resistant rejection of liver transplantation could recover after partial conversion from Tacrolimus to Sirolimus in practice (Song et al., 2006, 2008). It was also reported that Sirolimus could induce long-term immune tolerance (Hlavaty et al., 2015; Shan et al., 2014). How Sirolimus achieves these advantages over Tacrolimus is still unknown. As we know, regulatory lymphocytes guarantee human body to moderately offend “danger”, which induce immune tolerance and promote the long-term survival of the allograft. Regulatory T cells (Tregs) and regulatory B cells (Bregs) are important members of regulatory lymphocyte network, which can induce immune tolerance and lead to long-term allograft acceptance (Gorczynski et al., 2018; Li et al., 2015b; Manjarrez-Orduno et al., 2009; Peng et al., 2018; Savage et al., 2018). It was reported that Sirolimus could significantly stimulate the proliferation of Tregs in vivo and in vitro (Ghazal et al., 2018; Lewis et al., 2017; Royster et al., 2019; Strauss et al., 2007; Zhao et al., 2013). However, the effect of Sirolimus on Bregs was barely reported. In order to prevent tumor recurrence and alleviate nephrotoxicity, Tacrolimus was partially converted to Sirolimus in some liver transplant recipients in our center. In this study, we detected the changes of Bregs, Tregs and some relevant cytokines in peripheral blood among these patients. Furthermore, we compared the effects of Sirolimus and Tacrolimus on Bregs and Tregs by cell culture in vitro. The relevant cytokines in culture medium were neutralized in order to explore the possible mechanism of Sirolimus influencing regulatory lymphocyte.
Section snippets
Subjects
From January 2014 to December 2018, there were totally 22 liver transplant recipients who underwent partial immunosuppressive agent conversion from Tacrolimus to Sirolimus in our center. Among the 22 patients in the conversion group, 20 (90.9%) were males and the average age was 51.41 ± 7.38 years (with range of 31–63 years). 20 cases underwent drug conversion at the end of the first month after surgery in order to prevent tumor recurrence or renal function decline. The other two cases had drug
Effect of partial conversion from Tacrolimus to Sirolimus on the percentages of Bregs and Tregs in peripheral blood
Breg has the characteristics of phenotypic diversity. CD19+CD24+CD38+Bregs were detected in this study (Fig. 1A). In the conversion group, the percentages of Bregs and Tregs in total lymphocytes were both significantly increased in the first month after Sirolimus was adopted (P < 0.01 and P < 0.05) (Fig. 1B). However, in the observation period, no significant change of Bregs or Tregs was observed in the control group (Fig. 1C). IL-10+Bregs and TGF-β1+Bregs were further observed. The results
Discussion
Sirolimus is becoming popular among transplant recipients as a new immunosuppressive agent (Gullestad et al., 2016; Hamdy et al., 2019; Jeon et al., 2018; Tsai et al., 2019). In addition to preventing rejection in organ transplantation, it has shown to have the functions of anti-tumor, preventing aging and inducing immune tolerance (Kittipongdaja et al., 2015; Richardson, 2013; Wojarski et al., 2018). Sirolimus has many potential benefits through various biologic effects. But the detailed
Conclusion
In conclusion, partial conversion from Tacrolimus to Sirolimus can amplify Bregs and Tregs in liver transplant patient. Bregs may play an important role in Sirolimus amplifying Tregs by secreting IL-10 and TGF-β1 (Fig. 5). The increased regulatory lymphocytes and inhibitory cytokines are helpful in preventing rejection and biliary stenosis, even inducing allograft tolerance.
Funding
This work was supported by the National Natural Science Foundation of China (81771717).
Authors’ contributions
Bingyi Shi, Qian Lu and Jiyong Song designed the study; Jiyong Song, Guosheng Du and Bingyi Shi performed the operations; Wen Chen and Jiyong Song cultured the cells and collected the blood samples; Binyu Li detected the blood samples; Pengtao Bao analyzed the data; Jiyong Song wrote the paper; Qian Lu checked the paper. All authors read and approved the final manuscript.
Declaration of competing interest
All the authors declare no conflict interest of this study.
Acknowledgements
The authors would like to thank Ping Li, Li Xiao, Lili Bi and Yu Gao for their help.
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