An unanticipated role for survivin in organ transplant damage

Ischemia/reperfusion (I/R) injury is a major determinant of graft survival in kidney transplantation. Survivin, an inhibitor of apoptosis that participates in the control of mitosis and cell cycle progression, has been implicated in renal protection and repair after I/R injury; however, no study has been performed in the transplant setting. We investigated the role of survivin in modulating posttransplant I/R injury in syngeneic and allogeneic kidney grafts, and studied whether protection from I/R injury impacted on the recipient immune system, on chronic allograft nephropathy and rejection. We used genetically engineered mice with survivin haploinsufficiency and WT mice in which survivin over-expression was induced by gene-delivery. Survivin haploinsufficiency in syngeneic grafts was associated with exuberant I/R tissue injury, which triggered inflammation eventually resulting in graft loss. Conversely, survivin over-expression in the grafts minimized I/R injury and dysfunction in syngeneic grafts and in a clinically relevant fully MHC-mismatched allogeneic combination. In the latter, survivin over-expression translated into limited anti-donor adaptive immune response and less long-term allograft injury with protection from renal parenchymal damage. Our data support survivin over-expression in the graft as a novel target for protocols aimed at limiting tissue damage at the time of transplant ultimately modulating the recipient immune system.

Erythropoietin enhances immunostimulatory properties of immature dendritic cells

Dendritic cells (DCs) are the most potent antigen-presenting cells and play a crucial role by modulating the T cell immune response against infective agents, tumour antigens and alloantigens. The current study shows that differentiating bone marrow (BM)-derived DCs but not fully differentiated DCs are targets of erythropoietin (EPO). Indeed, DCs emerging from rat bone marrow, but not splenic DCs, express the EPO receptor (Epo-R) and respond to EPO stimulation displaying a more activated phenotype with increased CD86, CD40 and interleukin (IL)-12 expression levels and a higher allostimulatory capacity on T cells than untreated DCs. Moreover, results here presented show that EPO up-regulates Toll-like receptor (TLR)-4 in differentiating DCs rendering these cells more sensitive to stimulation by the TLR-4 ligand lipopolysaccharide (LPS). Indeed, DCs treated with EPO and then stimulated by LPS were strongly allostimulatory and expressed CCR7, CD86, CD40, IL-12 and IL-23 at higher levels than those observed in DCs stimulated with LPS alone. It is tempting to speculate that EPO could act as an additional danger signal in concert with TLR-4 engagement. Thus, EPO, beyond its erythropoietic and cytoprotective effects, turns out to be an immune modulator.