Peripheral blood regulatory T cell counts as a predictive biomarker for the outcome of kidney transplant: A systematic review.

Background And Objective: Circulating regulatory T cells could become a suitable biomarker for kidney recipients. The objective of this study was to evaluate the effect of mammalian target of rapamycin (mTOR) inhibitors on regulatory T cell numbers, and the clinical interest of this effect.

Material And Methods: Systematic review of published and unpublished studies. Worldwide databases or repositories. Randomised controlled trials and cohort studies comparing regulatory T cell counts and rejection episodes between patients with and without mTOR inhibitors were searched. Correlation of regulatory T cells-glomerular filtration rate might be supplied. Co-dependency regulatory T cells-mTOR inhibitors efficacy was evaluated.

Results: Five trials and 9 studies were included. Clinical differences made it difficult to obtain quantitative estimates of the effect of immunosuppression on regulatory T cell numbers. Nevertheless, we found that there are higher regulatory T cell numbers under treatment with sirolimus or everolimus. Rejection episodes were similar under calcineurin inhibitors and mTOR inhibitors despite different regulatory T cell numbers. Pooled correlation regulatory T cells-glomerular filtration rate was, prospectively 0.114 (95% confidence interval [95% CI] 0.062-0.406), and retrospectively 0.13 (95% CI 0.0-0.361). There is direct evidence although of low level (biomarker-stratified randomisation) on the co-dependency regulatory T cells-mTOR inhibitors efficacy.

Conclusions: Regulatory T cells counts may be associated with better outcomes under treatment with mTOR inhibitors (anti-rejection efficacy), considering that there is a relationship between these cells and kidney graft function.

Registration: PROSPERO (CRD42016046285).