Principles of Immunosuppression for Transplantation Organ transplantation involves replacing a diseased or dysfunctional organ with a healthy one from a donor. To prevent the recipient's immune system from rejecting the transplanted organ, immunosuppressive therapy is essential. Here are the key principles of immunosuppression in transplantation: 1. Purpose of Immunosuppression: Prevention of Rejection: • • Primary Goal: Suppressing the recipient's immune response to prevent rejection of the transplanted organ. Types of Rejection: Hyperacute rejection (immediate and severe), acute rejection (days to weeks post-transplant), and chronic rejection (months to years posttransplant). 2. Types of Immunosuppressive Agents: Induction Therapy: • • Purpose: Administered at the time of transplant to rapidly suppress the immune response. Agents: Antithymocyte globulin (ATG), basiliximab, or alemtuzumab. Maintenance Therapy: • • Purpose: Long-term suppression of the immune system to prevent rejection. Agents: Calcineurin inhibitors (tacrolimus, cyclosporine), antimetabolites (mycophenolate mofetil, azathioprine), and corticosteroids. 3. Mechanisms of Action: Calcineurin Inhibitors: • • Targets: Tacrolimus and cyclosporine inhibit calcineurin, preventing T-cell activation and interleukin production. Side Effects: Nephrotoxicity, hypertension, hyperglycemia. Antimetabolites: • • Targets: Mycophenolate mofetil inhibits purine synthesis, while azathioprine interferes with DNA synthesis in rapidly dividing cells. Side Effects: Bone marrow suppression, gastrointestinal disturbances. Corticosteroids: • • Targets: Prednisone suppresses inflammation and immune responses by modulating gene expression. Side Effects: Increased infection risk, osteoporosis, metabolic disturbances.