Immunological characteristics of renal transplant tolerance in humans

- B cell signature is strongly associated with tolerant state in kidney transplant.
- Regulatory properties of B cell subpopulations are descried in different cohorts of renal tolerant patients.
- T cell subsets are prone to pro-tolerogenic systemic environment in individuals with operational tolerance.
- Macrophages, natural killer cells, as well as dendritic cells and MDSC also participate in renal transplant tolerance.
- Knowing of immunological profile could shed a new light on the predictive biomarkers in allograft survival and rejection.

Establishing allograft tolerance is a highly desirable therapeutic goal in kidney transplantation, from which recipients would greatly benefit by withdrawing or minimizing immunosuppression. Identifying biomarkers in predicting tolerance or early diagnosing rejection is essential to direct personalized management. Recent findings have revealed that multiple populations of immune cells have involved in promoting long-term graft function or inducing rejection in renal transplant recipients. Thus, roles of immune cells add another level to predict the renal tolerant state; tailoring their functional and/or phenotypic characteristics would provide insights into mechanism involved in transplant tolerance that may aid in designing new therapies. Here, we review these findings and discuss the current understanding immunological characteristics of renal transplant tolerance in humans, and their potential clinical translation to immune tolerance biomarkers.