Biology · MU Sofia

34. Transplantation immunity. Host versus graft reaction. Types of transplants. Graft versus host reaction.

Covers transplantation terminology and the four graft types by source: autograft, isograft, allograft and xenograft. It then explains how T cells and antibodies drive rejection, the three T cell activation signals, and the four time-based rejection categories. Prevention through HLA matching and immunosuppression, immune tolerance, the fetus as a natural allograft, and graft-versus-host reaction with its three phases are also outlined. Four mnemonics are included to help recall the graft types, activation signals, rejection timing and GVHR phases.

Inside: 22 sections · 10 min

Topic 34 of 64 in the MU Sofia syllabus for Biology (Dental Medicine, Year 1). The free AceMed note covers it in 22 sections, about 1,365 words (10 min of reading).

In this note

  1. Transplantation immunity
  2. Understanding Transplantation
  3. Types of Grafts Based on Source
  4. The Immune Nature of Graft Rejection
  5. Mechanisms Behind Graft Rejection
  6. Cell-Mediated Immunity
  7. Pathways for Antigen Presentation
  8. Signals Required for T Cell Activation
  9. Role of Minor Histocompatibility Antigens
  10. Humoral (Antibody-Mediated) Immunity
  11. Types of Graft Rejection Based on Time Course
  12. Strategies for Preventing Graft Rejection
  13. HLA Matching
  14. Immunosuppressive Therapy
  15. Immune Tolerance in Transplantation
  16. The Fetus as a Natural Allograft
  17. Graft Versus Host Reaction (GVHR)
  18. Symptoms and Outcomes
  19. Preventive Measures
  20. Phases of GVHR
  21. Experimental and Emerging Therapies
  22. MNEMONICS

Understanding Transplantation

  • Transplantation refers to the process where a severely damaged body part is replaced by a healthy organ or tissue taken from another source.
  • The part that is transplanted is called a graft or transplant.
  • The organism providing the graft is known as the donor, while the one receiving it is called the recipient or host.
  • Although considered a last-resort treatment in many cases, transplantation has become increasingly important due to its life-saving potential.

Types of Grafts Based on Source

  • Autograft is a graft taken from one part of an individual's body and transplanted to another part of the same body. These grafts are always accepted because they are genetically identical to the host.
  • Isograft occurs between two genetically identical individuals, such as identical twins. These grafts are also accepted by the host immune system.
  • Allograft refers to a graft taken from another individual of the same species who has a different genetic makeup. This is the most common type and is typically rejected unless special measures are taken.
  • Xenograft is a graft taken from a different species. These are highly immunogenic and carry risks that are not fully understood. Porcine heart valves are one exception that are often used, but most xenografts are currently not suitable for human transplantation.

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