Skin allografts have been successfully used for temporary wound coverage in burn patients receiving conventional immunosuppressive drugs. With this procedure, unprecedented survival has been shown when 90% mortality was expected. Cyclosporine (CyA), a powerful new immunosuppressive agent, could provide a more effective method to enhance skin allograft survival in burn patients. By using CyA and allografted skin, completely healed burn wounds could be obtained in days rather than weeks. To study the feasibility of this concept, we will investigate the following in a rat burn model: 1. CyA's effect on animal survival in combination with a 50% body surface area thermal injury. 2. CyA's effect on the survival of rat skin allografts transplanted across a strong histocompatibility barrier in the rat burn model. 3. The immune responsiveness of thermally injured rats undergoing skin transplantation, CyA therapy, and bacterial challenge (both systemic and topical challenge). 4. Possible toxicity associated with CyA therapy. 5. Simple, efficient, and predictable quantitative methods to monitor the rejection process. Thus, CyA's effectiveness in prolonging skin transplant survival in rats undergoing massive thermal injury will be delineated. In addition, the immune response of rats receiving CyA treatment will be studied in an effort to understand whether CyA totally suppresses the immune response or only selectively suppresses it, thus allowing immune responsiveness against bacterial infection.