W12.1 Flashcards
Transplantation
a act of transferring cells, tissue, or organ from one site to another
Graft
Implanted cell, tissue or organ
Donor
Individual who provides the graft
Recipient/host (transplantation)
Individual who receives the graft
Relevance of transplantation
Potentiallylifesavingtreatment for:
- Organ failure
- Cancer
- Autoimmunity
- Immune deficiencies § Burns
Types of transplants
Autograft, Xenograft, Isograft, Allograft
The problem with transplantation
Transplant contains foreign tissue containing Antigens (Ag) that can induce a damaging immune response: graft rejection or GVHD
Transplantation Antigens
Just like the flu virus would, alloantigens elicit both
- cell-mediated and § humoral (antibody) immune responses,
- Recognition of whether transplanted cells are self or foreign is determined by Transplantation Antigens
- Major histocompatibility complex (MHC) Ags (HLA)
- Minor histocompatibility Ags (mHAs)
- ABO Blood Group Ags
- MHC class I-related chain A (MICA) Ags
MHC AG (transplantation)
MHC/HLA Antigens are encoded by several genes: HLA-A, B and C and HLA-DP, DQ, DR
- Genes are polymorphic and inherited (one from each parent) as a haplotype
- Donor/Recipient haplotype should match
Direct vs Indirect Allorecognition (P12)
???
Rejection Effector mechanisms (for organ transplant)
- Hyperacute
- Acute
- Chronic
Hyperacute Rejection
- Minutes to hours
- Mediated by recipient’s preformed antibody
- Abs against ABO, HLA, and certain endothelial antigens
- Abs bind to tissue and activate C, destroying tissue
- Rare due to prescreening for Abs
Acute cellular rejection
- weeks after transplant
- cellular-type T cell-mediated rejection but may also involve antibodies
- MHC mismatch–> faster acute rejection
- mHA mismatchà slower acute rejection
Chronic rejection
graft arteriosclerosis with progressive fibrosis and scarring with narrowing of the vessel lumen due to smooth muscle cell proliferation
