Tolerance in Heart Transplantation: The Holy Grail, or an Attainable Goal?

Helminths and immunological tolerance

Current immunosuppression regimens for solid-organ transplantation have shown disappointing efficacy in the prevention of chronic allograft rejection and carry unacceptable risks including toxicity, neoplasia, and life-threatening infection. Achievement of immunological tolerance (long-term antigen unresponsiveness in an immunocompetent host) presents the exciting prospect of freedom from immunosuppression for transplant recipients. It is now 60 years since the first demonstration of immunological tolerance in animal models of transplantation, but translation into routine clinical practice remains elusive. Helminth parasites may provide novel strategies toward achieving this goal. Helminths are remarkably successful parasites: they currently infect more than one quarter of the world’s population. It is now well established that the parasites’ success is the result of active immunomodulation of their hosts’ immune response. Although this primarily secures ongoing survival of the parasites, helminth-induced immunomodulation can also have a number of benefits for the host. Significant reductions in the prevalence of allergy and autoimmune conditions among helminth-infected populations are well recognized and there is now a significant body of evidence to suggest that harmful immune responses to alloantigens may be abrogated as well. Here, we review all existing studies of helminth infection and transplantation, explore the mechanisms involved, and discuss possible avenues for future translation to clinical practice.

The changing face of heart transplantation

It has been 40 years since the first human-to-human heart transplant performed in South Africa by Christiaan Barnard in December 1967. This achievement did not come as a surprise to the medical community but was the result of many years of early pioneering experimental work by Alexis Carrel, Frank Mann, Norman Shumway, and Richard Lower. Since then, refinement of donor and recipient selection methods, better donor heart management, and advances in immunosuppression have significantly improved survival. In this article, we hope to give a perspective on the changing face of heart transplantation. Topics that will be covered in this review include the changing patient population as well as recent advances in transplantation immunology, organ preservation, allograft vasculopathy, and immune tolerance.