Prognostic significance of graft Foxp3 expression in renal transplant recipients: a critical review and attempt to reconcile discrepancies.

A large body of evidence has been accumulated from experimental models in the past decade to support the critical role of Foxp3-expressing regulatory T cells (Tregs) in the suppression of alloimmune responses. This has prompted transplant clinicians to investigate whether Foxp3 analysis might be used as an immunodiagnostic tool for better assessment of the significance of graft infiltrate and to predict its impact on graft outcome. However, conflicting results have emerged from these studies and may have generated more confusion than clarification. Foxp3 expression has been antagonistically correlated with either good or poor prognosis. We discuss here how methodological issues and specific clinical settings may have accounted for the discrepancies between the results of these studies. Depending on many factors, including the techniques used, the method of sampling normalization, the extent of intra-graft inflammation, the immunosuppressive regimen and the depletion or repletion of T lymphocyte compartment, the significance of Foxp3 expression may vary. We propose here the conditions to be fulfilled in order to use Foxp3 analysis as a relevant biomarker for graft outcome assessment. Far from challenging the key role of Tregs in dampening alloimmune responses, this review highlights the need for technical harmonization and standards.

Bridging innate with adaptive immunity in transplantation: triggers, sensors, and modulators.

The molecular entities present on a cell or organ transplant that trigger the innate immune response and link to the adaptive immune system are increasingly recognized as a key influence on early graft function and for determining the microenvironment that will guide longer-term graft outcomes. The 2014 Beaune Seminar in Transplant Research discussed the evidence for triggers, sensors, and modulators of innate and adaptive immunity in response to alloantigens, challenged the conventional view, developed novel hypotheses, and highlighted the potential for therapeutic manipulation of these responses.