What is an allograft rejection?
Allograft rejection is the consequence of the recipient’s alloimmune response to nonself antigens expressed by donor tissues. After transplantation of organ allografts, there are two pathways of antigen presentation.
What causes allograft rejection?
Acute rejection is caused by the mismatch in highly polymorphic human leukocyte antigens (HLA) and is mediated primarily by T cells. They produce cytokines upon activation, which recruit inflammatory cells eventually leading to necrosis of graft tissue.
What is the mechanism for the rejection of tissue grafts?
The ability of recipient T cells to recognize donor-derived antigens, called allorecognition, initiates allograft rejection. Once recipient T cells become activated, they undergo clonal expansion, differentiate into effector cells, and migrate into the graft where they promote tissue destruction.
What is a chronic allograft rejection?
Chronic graft rejection (CGR) of solid organs is defined as the loss of allograft function several months after transplantation. The transplanted organ may still be in place, but persistent immune system attacks on the allo-MHC expressed by its component cells have gradually caused the organ to cease functioning.
How can we prevent allograft rejection?
Suppressing the immune response may prevent transplant rejection. Medicines will likely be used to suppress the immune response. Dosage and choice of medicines depends on your condition. The dosage may be very high while the tissue is being rejected.
What are the types of rejection?
There are three types of rejection:
- Hyperacute rejection occurs a few minutes after the transplant when the antigens are completely unmatched.
- Acute rejection may occur any time from the first week after the transplant to 3 months afterward.
- Chronic rejection can take place over many years.
What is the molecular basis of allograft rejection?
The main antigens responsible for driving rejection are the major histocompatibility complex (MHC) molecules. MHC class I molecules are constitutively expressed by all nucleated cells and present intracellular epitopes to CD8 + cytotoxic T-cells.
What is the cause of acute allograft rejection?
Acute allograft rejection is caused primarily by the infiltration of T cells into the allograft, which triggers inflammatory and cytotoxic effects on the graft.
What happens to an allograft after a transplant?
During healing of allograft, revascularization and osteoclastic activity would ideally result in eventual replacement of the allograft with host bone, eliminating the original defect. If this revascularization and replacement were observed in another tissue organ transplant, it would be analogous to classic graft rejection.
What are the different types of graft rejection?
•Compare and contrast the various types of graft rejection: -Hyper acute rejection. -Acute rejection. -Insidious rejection. -Late rejection.
Are there isografts that do not activate a rejection response?
Similarly, isografts between isogeneic (genetically identical) individuals, such as monozygotic (identical) twins or mice of the same inbred strain, do not express antigens foreign to the recipient and so do not activate a rejection response.