Basics of immune responses in transplantation in preparation for application of composite tissue allografts in plastic and reconstructive surgery: Part I

Learning Objectives: After studying this article, the participant should be able to: 1. Understand the role of major histocompatibility complex molecules, T cells, antigen-presenting cells, and natural killer cells in the process of allograft acceptance and rejection. 2. Understand the mechanism and differences of acute and chronic allograft rejection. 3. Be familiar with modern immunosuppressive protocols and their applicability to composite tissue allografts transplants. 4. Be familiar with risks and side effects of different immunosuppressive protocols. 5. Outline the application of composite tissue allograft transplants in plastic and reconstructive surgery. Summary: Currently, composite tissue allografts are applied only occasionally as a reconstructive option in the field of plastic and reconstructive surgery. Composite tissue allografts offer a unique potential for coverage of large multitissue defects. However, compared with the relatively homogenous tissue of solid organ transplants, the heterogenicity of tissue components of composite tissue allografts may generate high immunologic responses. Modem immunosuppressive agents significantly improve successful allograft acceptance. However, chronic allograft rejection and immunosuppressive drug toxicity are still major problems in the clinical practice of transplantation. The major goals of transplantation immunology are (1) to develop tolerance to allograft transplants and (2) long-term drug-free survival. A number of experimental protocols were designed to develop tolerance; however, none of them has been proven to induce tolerance in clinical transplantation. In this article, the authors outline the mechanisms of allograft acceptance and rejection and barriers to transplantation tolerance. Novel immunosuppressive protocols are discussed in this review. This basic immunologic knowledge of allograft acceptance and rejection will allow plastic surgeons to apply composite tissue allograft transplants to plastic and reconstructive surgery.