Exam 2: Transplantation Flashcards
Autograft
(Autologous)
Self-tissue transferred from one site of the body to another on the same individual.
Histocompatible.
Isograft
(Syngeneic)
Tissue transferred between genetically identical individuals.
(E.g. monozygotic twins)
Histocompatible.
Allograft
Tissue transferred between genetically different members of the same species.
Histoincompatible.
Xenograft
Tissue transferred between members of different species.
Histoincompatible.
Histocompatible
A tissue that is antigenically similar to the recipient’s tissue and does NOT induce an immunological response that leads to tissue rejection.
Histoincompatible
A tissue that is antigenically dissimilar to the recipient’s tissue and induces an immunological response that leads to tissue rejection.
- There are 40 other factors affecting histocompatibility other than ABO, Rh, and HLA.
- All transplants are histoincompatible except for autograft or isograft
Transfusion
Involves the transfer of blood from one individual to another.
Transplantation
Types
Involves the transfer of any organ or tissue from one individual to another.
- Whole organs: kidney, liver, lung, heart, pancreas etc.
- Tissues: bond, skin, cornea etc.
- Cellular: bone marrow, pancreatic islet cells etc.
Histocompatibility
Genes
-
ABO antigens
- Most important parameter in solid organ grafts
- Blood group type can change with bone marrow transplantation
-
MHC/HLA
- Matching class II MHC important in solid organ transplant
- Must match both class I and II for bone marrow transplantation
-
Minor histocompatibility antigens
- > 40 different genes important in preventing rejection
Graft-versus-Host
(GvH)
- Follows transfer of immunologically competent alloreactive lymphocytes into an immunocompromised host
- Bone marrow transplant
- Passenger lymphocytes in an organ
-
Graft mounts an immunological attack on the host
- CD4 T-cells ⇒ promote damaging immune function
- CD8 T-cells ⇒ destroys tissue
- Host cells can aid donor cells in tissue destruction
-
Preventative measures:
- Removal of T cells using T-cell reactive mAb and complement
- ↓ incidence and severity of GvH
- However, if bone marrow purged completely of competent T-cells using anti-CD3+ complement treatment
- ↑↑↑ engraftment failure
- Removal of T cells using T-cell reactive mAb and complement
- Occurs even in HLA matched siblings and during autologous transplants
Acute GvH
Symptoms
- Epithelial cell necrosis of skin, liver, and GI tract
- Rash
- Jaundice
- Diarrhea
Chronic GvH
Symptoms
- Fibrosis of skin, liver, and/or GI tract without necrosis
- Can lead to complete organ dysfunction
Host-versus-Graft
(HvG)
- Alloreactive host lymphocytes damages the graft
- Follows transplantation of a histoincompatible tissue organ
- May lead to destruction of the organ
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Allograft Rejection
Types
Host-versus-graft reactions following solid organ transplants:
- Hyperacute rejection
- Acute rejection
- Chronic rejection
Hyperacute Rejection
Occurs within minutes to ~12-24 hours post-reperfusion of the organ.
Type II hypersensitivity.
Preformed Ab binds to tissues → complement activation → recruitment of phagocytic cells, platelet activation and deposition → thrombosis, swelling, hemorrhage, and necrosis
- Cell-mediated immunity is generally NOT involved
- Characterized by thrmobotic occlusions with endothelial injury, neutrophil influx, and fibrinoid necrosis
-
No treatment
- Only prevention
- ABO matching
- PRA screening for pre-existing Ab
- Cross matching
- Only prevention