Tissue and organ transplants are now fairly common medical procedures encountered by pediatric nurses practicing in acute care settings. The understanding of what is known about the immune response to foreign antigens provides strong evidence of the immunologic barriers to organ and tissue transplantation. It is known that failure to suppress this immune response will result in degradation of transplanted organs and tissue. The extent to which these processes occur will depend on the action of T cells. Specific control of T cell action depends on the immunosuppressive agents administered. Administration of one or more of the identified iatrogenic immunosuppressive agents, at varied intervals and in varied doses, will surely affect the outcomes of the transplant process. Caring for children undergoing such a procedure requires an indepth knowledge of immune system function, as well as the various pharmacologic therapies employed.