Oral alloantigen exposure promotes donor-specific tolerance in a mouse model of minor mismatched skin transplantation

Abstract

Abstract Oral tolerance is a powerful, non-invasive route to induce immune tolerance, yet it has been unsuccessful to promote graft acceptance in rodent models of transplantation. To this end, we developed a mouse model where the model antigen ovalbumin (OVA) was introduced orally, in a regimen designed to improve bioavailability, duodenal lymph node drainage and prolong duration of antigen exposure, prior to transplantation with skin grafts constitutively expressing membrane-bound OVA. We found that oral OVA treatment pre-transplantation promoted permanent graft acceptance as well as linked tolerance to skin grafts expressing OVA coupled to the additional model antigen 2W. Tolerance was donor-specific, as secondary donor-matched, but not third-party grafts were spontaneously accepted in the absence of additional immunosuppression. Treatment with this oral OVA regimen promoted an anergic phenotype in OVA-reactive CD8+ T cells, generation of iTregs, and dysfunction of OVA-reactive CD4+ T cells pre-transplantation. The tolerance induced by oral OVA was robust, as anti-CD25/anti-PD-L1 at the time of transplantation failed to prevent skin graft acceptance. Mechanistically, we revealed a critical role for the proximal gut draining lymph nodes (gLNs) in mediating this effect, as an intestinal infection that drains to the proximal gLNs prevented the induction of transplantation tolerance. Our study extends previous work applying oral antigen exposure to transplantation and serves as proof of concept that the systemic immune mechanisms supporting oral tolerance are sufficient to promote long-term graft acceptance. Regimens that improve bioavailability and duration of oral alloantigen administration may hold promise in the clinic. This work was supported by a NIAID grant to ASC and MLA (P01AI-97113). Peter Wang was supported by undergraduate research grants from the Katen Scholars Program and the Dean's Fund for Undergraduate Research.