Dr. O’Connor is focused on the immunological aspects of heart transplantation in children, specifically the impact of anti-HLA antibodies. Anti-HLA antibodies are a major source of rejection following heart transplantation. Although these antibodies are absent in many patients, their presence can complicate or even prevent a transplant from happening; therefore, reducing or eliminating them before transplant is very important in order for the patient to receive a heart that is compatible with his or her immune system.