"Organ transplantation is technically challenging, it is an intense area of research, and it involves nearly every discipline," he said. "Most of all, it is rewarding on a personal level. It's so gratifying to see patients after transplantation; to see the physical and emotional transformations."

These are patients who have spent the last year or more struggling just to stay alive, fighting the killing effects of end-stage disease. Because of the complexity of these operations and the attendant risks, patients must be in the end stage of their disease to be candidates.

As a member of the UCSD renal transplant team, Hart's responsibilities reach far beyond the operating room. In truth, while the actual transplant is a major event for the patient, it is only a piece of the much larger patient-care picture.

"This field provides the rare opportunity to be actively involved in the total care and management of patients with complex conditions before, during, and after the operation," he said. "From a clinical perspective, it is one of medicine's most challenging, stimulating, and broad-based environments."

Multiorgan transplant programs, such as the one at UCSD, are yielding tremendous amounts of new information on the structure and function of organ systems, the biology of rejection, organ preservation, and regeneration. There is a virtual explosion of information that is benefiting not only transplant recipients, but thousands who suffer from irreversible disease of a vital organ.

Yet, for all that is known, there are many questions still to be answered, making it a fertile field for research.

For example, so much about the human immune system remains a mystery. Why does a transplanted kidney require major antirejection drug therapy to control the immune system's attack, while a transplanted liver requires very little? What is chronic rejection, which, unlike acute rejection, cannot be reversed with immunosuppression therapy?

Working to find the answers to these types of questions is what makes Hart tick.

"It is an exciting time to be in this field," he said. "Right now, we're looking at new drugs and developing immunosuppression strategies that we hope will improve graft (donor organ) survival."

At every turn, it seems, there's intellectual stimulation, professional challenge, and personal gratification for Marquis Hart.

"That's what brings me to work everyday."