Transplant Immunology

Research activities in transplantation and transplant immunology at Penn Vet and Penn Medicine have contributed significantly to the current successful outcomes of organ transplantation.

Patients require an organ transplant when their own organs no longer function properly due to advanced disease or congenital disorders. Different organs can be transplanted including kidney, heart, lung, liver, pancreas, and intestine. The process involves surgically removing the organ from a living healthy donor (as for kidney transplants) or a donor who has recently died but who has an otherwise healthy functioning organ (for example heart and lungs) and surgically implanting it (transplant) into the patient with organ failure. The healthy organ then takes over the function of the diseased organ and enables the patients to live more normal lives.

Native kidney

Penn Vet has been at the forefront of feline kidney (renal) transplant medicine for over 25 years. Dr. Lillian Aronson has performed over 185 renal transplants in cats with kidney failure, through a highly successful feline renal transplant program (include link to renal transplant page).

Successful organ transplantation in dogs has been more challenging. Like humans, the major challenge is prevention of organ rejection which is mediated by the recipient’s immune system. Discovering ways to suppress immune-mediated rejection without causing significant morbidity and/or mortality in human and canine patients is the holy grail of transplant medicine and would be significant advance for transplantation in both species. The unique expertise of Drs. Raimon Duran-Struuck and Jim Riley  in transplantation immunology and their exploration of cellular therapies to induce transplant tolerance aims to improve outcomes for human and canine transplant patients.


  • Why does the body reject transplanted organs?

    During development, the developing immune system is educated to distinguish between cells that belong to that organism versus those that are “foreign” or do not belong to that particular organism. As such, the immune system is programmed to attack “non-self” agents and cells which include infectious organisms such as bacteria and viruses, as well tissues from other organisms, including organs that might be needed for transplant. Therefore, because transplant organs come from other individuals they are considered to be “foreign” by the immune system and will be rejected by the patient’s immune

  • What is done to prevent organ rejection?

    Since the patient’s immune system is responsible for rejecting foreign tissues and organs, the mainstay of treatment to prevent organ rejection is immune suppression. Immune suppression is usually achieved by using drugs such as prednisone and cyclosporine.

  • What are the side effects of immune suppression?

    Current immune suppressive drugs used to prevent immune rejection of organ transplants cause widespread immune suppression which makes the patient susceptible to systemic infections, and can increase the incidence of cancer. In addition, immune suppressive drugs such as prednisone have additional side effects including increasing thirst, appetite, muscle weakness, and weight gain.

  • What are novel approaches to successful transplant?

    Cellular therapies that induce immune “tolerance” to the transplanted organ or graft are being actively investigated. These may include the use of the patient’s own immune cells known as regulatory T cells (that regulate the immune response) as well as cells from a healthy donor known as invariant NKT cells (iNKT cells) that can mediate their own immune tolerance as well as provide tolerance to a transferred graft.