Please enable JavaScript.
Coggle requires JavaScript to display documents.
TRANSPLANT IMMUNOLOGY, SANDHYA A 191822016 - Coggle Diagram
TRANSPLANT IMMUNOLOGY
DEFINITON
The complex mechanisms of immunity, which under normal circumstances work to identify foreign microbes and direct the immune system to destroy them, pose a significant barrier to successful transplantation.
Rejection of a transplant occurs in instances where the immune system identifies the transplant as foreign, triggering a response that will ultimately destroy the transplanted organ or tissue.
TYPES OF TRANSPLANTATION
Autograft –Transplantation of cells, tissues or organs between sites within the same individual e.g. skin graft.
Allograft – Transplantation of organs or tissues from a donor to a non-genetically identical individual of the same species. Allografts are the most common type of transplant.
Xenograft – Transplantation of an organ or tissue between two different species. ‘Pig valves’, for example, are commonly used to repair or replace a defective heart valve in humans.
ABO incompatible – ABO refers to blood group, which can vary between individuals. For most transplant types, matching of blood group between donor and recipient is a key strategy in reducing rejection risk.
Stem cell transplant – Stem cells are cells that have the capacity to develop into a range of different types of cells in the body.
SELF AND NON SELF
When the immune system encounters a foreign organism, it mounts an attack against it to protect the body from infection. To prevent an attack on our own cells and tissues (autoimmunity), the immune system must be able to differentiate between our own healthy tissues and foreign invaders.
MECHNISM OF REJECTION
Graft rejection occurs when the recipient’s immune system attacks the donated graft and begins destroying the transplanted tissue or organ. The immune response is usually triggered by the presence of the donor’s own unique set of HLA proteins, which the recipient’s immune system will identify as foreign.
In some cases, a patient may experience something known as ‘graft versus host reaction’ where mature immune cells already present in the donor graft begin attacking the healthy cells of the recipient.
-
DONOR-RECIPIENT MATCH
ABO blood group compatibility – The donor and recipient are tested for compatible blood groups. This is the first test to be carried out as the transplant will be rapidly rejected if the blood groups do no match. In some transplants
Tissue typing – A blood sample is taken from the recipient to identify the HLA antigens present on the surface of the their cells to help find a histone compatible donor.
Cross matching – Blood samples are taken from both the recipient and donor, and the cells of the donor are mixed with the blood serum of the recipient.
Panel reactive antibody test – The blood serum of patients awaiting transplantation are tested for reactive antibodies against a random panel of cells.
Serology screening – For patients undergoing stem cell transplantation they and their donor will undergo pre-transplant serology screening.
Immunosupressive drugs
Immunosuppressive drugs are given in two phases; an initial induction phase involving a high dose, and a later maintenance phase which involves using the drug in the long term at a lower dose.
All current immunosuppressive drugs come with limitations. One of the major limitations of these drugs is immunodeficiency.
A fine balance needs to be reached between suppressing immune function sufficiently to avoid rejection, preventing drug toxicity, and maintaining enough immune function to fight off disease.
-
-