Unit
- Immune function basics: The immune system distinguishes self from non-self, targeting foreign cells and molecules. In transplantation, the recipient immune system recognizes the donor organ as foreign, triggering a response that can lead to rejection if not managed.
- Types of immune cells: T cells and B cells play central roles in rejection. T cells directly attack graft cells, while B cells produce antibodies against donor antigens. Understanding these cells helps operational staff appreciate why immunosuppression is needed.
- Major histocompatibility complex (MHC): In humans, MHC molecules are called human leukocyte antigens (HLA). They present peptides to T cells; differences between donor and recipient HLA trigger strong immune responses. This concept is foundational for tissue typing.
- Rejection categories: Hyperacute rejection occurs minutes to hours post-transplant due to pre-existing antibodies. Acute rejection happens weeks to months later, mediated by T cells. Chronic rejection develops over months to years, involving both immune and non-immune factors.
- Immunological memory: After exposure, the immune system remembers antigens, leading to faster and stronger responses upon re-exposure. This impacts retransplantation and requires careful antibody monitoring.
- Role of complement system: Complement proteins enhance antibody-mediated damage and inflammation. Their activation contributes to tissue injury during rejection episodes.
- Operational relevance: Transplant coordinators and administrators do not need deep immunology research skills, but they must understand basic concepts to interpret lab results, explain risks to patients, and coordinate care with immunologists.
- Patient education: Explaining immune response in simple terms helps patients comply with immunosuppressive regimens and recognize signs of rejection. Operations staff should be able to provide this education.
- Costimulation and T cell activation: For full activation, T cells require two signals: antigen recognition through the T cell receptor and a costimulatory signal from antigen-presenting cells. Without costimulation, T cells become unresponsive or anergic. This concept helps operations staff understand why drugs like belatacept, which block costimulation, are used to prevent rejection while sparing some immune function.
- Induction therapy: Induction therapy involves administering potent immunosuppressive agents immediately after transplant to prevent early rejection. Common agents include lymphocyte-depleting antibodies like antithymocyte globulin or IL-2 receptor blockers like basiliximab. Operations staff must be aware of dosing schedules and potential side effects such as infusion reactions and increased infection risk.
- Crossmatch testing: Before transplant, a crossmatch test mixes recipient serum with donor lymphocytes to detect pre-existing anti-donor antibodies. A positive crossmatch indicates a high risk of hyperacute rejection and typically prevents proceeding with that donor. This test is essential for safe donor-recipient matching and must be interpreted quickly by the transplant team.
Terminology
- Antigen
- A molecule that can be recognized by the immune system, often a protein on the surface of cells.
- Antibody
- A protein produced by B cells that binds specifically to an antigen, marking it for destruction.
- Allograft
- An organ or tissue transplanted from one individual to another of the same species.
- Immunosuppression
- The reduction of immune system activity, typically through medication, to prevent rejection.
Quick Revision
- Immune system distinguishes self from non-self; transplanted organs are seen as foreign.
- T cells and B cells are key players in rejection; HLA molecules drive immune recognition.
- Rejection types include hyperacute, acute, and chronic, each with different timeframes and mechanisms.
- Basic immunology knowledge helps operations staff communicate effectively and support patient care.