delivery of regulatory T-cells for control of alloimmune priming in the donor lung.

Background: Survival after lung transplantation (LTx) is hampered by uncontrolled inflammation and alloimmunity. Regulatory T-cells (Tregs) are being studied as a cellular therapy in solid organ transplantation. Whether these systemically administered Tregs can function at the appropriate location and time is an important concern. We hypothesised that -expanded recipient-derived Tregs can be delivered to donor lungs prior to LTx lung perfusion (EVLP), maintaining their immunomodulatory ability.

Methods: In a rat model, Wistar Kyoto (WKy) CD4CD25 Tregs were expanded prior to EVLP. Expanded Tregs were administered to Fisher 344 (F344) donor lungs during EVLP; left lungs were transplanted into WKy recipients. Treg localisation and function post-transplant were assessed. In a proof-of-concept experiment, cryopreserved expanded human CD4CD25CD127 Tregs were thawed and injected into discarded human lungs during EVLP.

Results: Rat Tregs entered the lung parenchyma and retained suppressive function. Expanded Tregs had no adverse effect on donor lung physiology during EVLP; lung water as measured by wet-to-dry weight ratio was reduced by Treg therapy. The administered cells remained in the graft at 3 days post-transplant where they reduced activation of intra-graft effector CD4 T-cells; these effects were diminished by day 7. Human Tregs entered the lung parenchyma during EVLP where they expressed key immunoregulatory molecules (CTLA4, 4-1BB, CD39 and CD15s).

Conclusions: Pre-transplant Treg administration can inhibit alloimmunity within the lung allograft at early time points post-transplant. Our organ-directed approach has potential for clinical translation.