Treg-based therapy and mixed chimerism in small intestinal transplantation: Does Treg+BMT equal intestine allograft tolerance?

Association between oral nutrition and inflammation after intestinal transplantation

Intestinal transplantation (Itx) can be a life-saving treatment for certain patient populations, including those patients with intestinal failure (IF) who develop life-threatening complications due to the use of parenteral nutrition (PN). Most patients who have undergone Itx are eventually able to tolerate a full oral diet. However, little guidance or consensus exists regarding optimizing the specific components of an oral diet for Itx patients, including macronutrients, micronutrients and dietary patterns. While oral dietary prescriptions have moved to the forefront of primary and preventive care, this movement has yet to occur across the field of organ transplantation. Evidence to date points to the role of systemic chronic inflammation (SCI) in a wide variety of chronic diseases as well as post-transplant graft dysfunction. This review will discuss current trends in oral nutrition for Itx patients and also offer novel insights into nutritional management techniques that may help to decrease SCI and chronic disease risk as well as optimize graft function.

Update on Chronic Rejection After Intestinal Transplant: An Overview From Experimental Settings to Clinical Outcomes

Chronic rejection affects the long-term survival of solid-organ transplants, accounting for an incidence of between 5% and 10% after intestinal/multivisceral transplant. Because of unclear symptoms and signs and endoscopic findings, the diagnosis is often delayed. Presently, allograft removal represents the only available therapy due to the absence of effective pharmacologic approaches. Extensive research, through animal models, has been performed over the past 20 years to clarify the complex immune- and nonimmune-mediated mechanisms behind the development of chronic allograft enteropathy, with the aim of elucidating how to avert chronic rejection. The role of donor-specific antibodies and the way to challenge them in the clinic have gained acceptance among transplant centers as one of the main steps to prevent chronic rejection, although no common protocol exists that can be applied in a systematic fashion. The adjunct of a liver graft when retrans planting is needed in a sensitized recipient due to its protective effect against humoral immunity. Multicenter studies and clinical trials are required to better understand the pathogenesis of chronic rejection and to find the therapeutic answer to this clinical query.

Donor-Specific Regulatory T Cells Acquired from Tolerant Mice Bearing Cardiac Allograft Promote Mixed Chimerism and Prolong Intestinal Allograft Survival

The induction of donor-specific transplant tolerance has always been a central problem for small bowel transplantation (SBT), which is thought to be the best therapy for end-stage bowel failure. With the development of new tolerance-inducing strategies, mixed chimerism induced by co-stimulation blockade has become most potent for tolerance of allografts, such as skin, kidney, and heart. However, a lack of clinically available co-stimulation blockers has hindered efficient application in humans. Furthermore, unlike those for other types of solid organ transplantation, strategies to induce robust mixed chimerism for intestinal allografts have not been fully developed. To improve current mixed chimerism induction protocols for future clinical application, we developed a new protocol using donor-specific regulatory T (Treg) cells from mice with heart allograft tolerance, immunosuppressive drugs which could be used clinically and low doses of irradiation. Our results demonstrated that donor-specific Treg cells acquired from tolerant mice after in vitro expansion generate stable chimerism and lead to acceptance of intestinal allograft. Increased intragraft Treg cells and clonal deletion contribute to the development of SBT tolerance.