Flashcards in Transplant Immunology Deck (45):
What is an alloantigen ?
Antigen which varies between members of the same species
What is an alloreaction ?
Immune responses directed atainst alloantigens
What are immunogenetics ?
A subfield of immunology devoted to the genetics of alloantigens
What is an autograft ?
A graft of tiddue from one site to antoher site on the same individual
What is a Synergic graft ?
A graft of tissue from one individual to another individual that is genetically identical
What is an allograft ?
Graft of tissue from one person to another person that is genetically different
What are the three basic problems associated with transplantation of tissue ?
1. It must perform its basic function
2. Health of the donor and recipient must be maintained during the operation
3. The immune system of the recipient must accept the transplantation
What are the most important genes involved with transplant rejection ?
The HLA haplotype
Do RBC's express MHC-1 or MHC-2
What causes alleoreactions with blood transfusions ?
The alloreactions are based on the structural polymorphisms in the carbohydrates on glycolipids of the erythrocytes
What is the most common basis of alloreactivity to a graft produced by a recipients immune system ?
The difference in HLA expression on the erythrocyte surface. These differences are related to the A, B, O blood system
Is the blood surface glycoprotein similar to the surface antigen of bacteria ?
Yes. and because the surface carbohydrates are similar most people will have produced antigens specific
How would the body react against the foreign blood RBC's
A person that has type O blood receives a transfusion of they A or type B blood that person's Anti-A or Anti-B antibodies will attack the foreign blood types.
How is HLA polymorphic ?
There are many different alleles of the MHC class 1 molecule
What will happen if a person's Anti-A or Anti-B antibodies bind to an RBC that they deem foreign ?
The Anti-A or Anti-B antibodies will activate the complement cascade and cause the Blood type. This will result in fever, chills, shock, renal failure, and sometimes death.
What is an Rh factor ?
A polymorphic blood antigen that are polymorphic with regard to the population
What is the most important Rh factor with regard to blood transfusion ?
The RhD factor
Is there any other antigen similar to the Rh antigen that the body could be sensitized to ?
No, unlike the ABO there are no structures on normal flora bacteria that are similar to the RhD. Therefore if people do not have Rh + blood they will not have an antibody sensitized to the Rh factor.
What would happen if an ( Rh - ) person was sensitized to the Rh factor receives blood from the ( Rh + ) donor
There would be life threatening blood reaction
Can a fetus have a different haplotype of MHC antigens from the mother.
Yes the fetus is essentially an allograft
What will happen if a mother (Rh-) gives birth of the baby who has a different Rh factor from her ?
The Rh - mother will be sensitized to the Rh factor and produce the Rh antibody. If the mother is exposed to Rh+ blood another time she will illicite the complement induced degradation of the blood that is foreign.
Does the placenta have MHC-1 on it ?
No it forms a barrier between the fetus and the mother's T cells
Does the trophoblast express cytokines, If yes what do they do ?
Yes the tropoblast expresses cytokinesthat produce Th2 cytokines. They promote Ab responses and depress T cell responses.
When you have a woman who is Rh- and she has had a baby that caused her to be sensitized to the Rh factor how will you treat her if she is pregnant with another Rh+ baby ?
You give her Rhogam which is a preparration of Ab's that are specific for RhD+ erythrocytes and will thus trigger their destruction.
Is is possible to prevent themother from generating the Rh sensitization following the birth of a Rh+ fetus ?
Yes if RhoGam is given right after the birth then she will not be sensitized to the Rh factor
When is Rhogam treatment started when a woman is pregnant ?
6 Months into the pregnancy
Are ABO antigen s expressed on endothelial cells ?
Yes. and they play a key role in the acute transplantation rejection .
What will happen if a person with Type O blood receives a transplant from a person who has type A blood ?
The patient's Anti-A antibodies will cause a rejection of the tissue
How would a rejection occure if the transplanted tissue had ABO antigens on the endothelial cells that the recipient was sensitized to ?
The complement system would be activated through the classical pathway and the graft rejection would occur in 12-48 hours.
Can HLA antigens mediate hyper-acute graft rejection ?
YesHLA antigen scan also mediate hyperacute graft rejection. Anti-HLA Ab's can be generated in the recipient as a result of immune response to a previous pregnancy, blood transfusion, or previous tissue graft.
How do you gauge the degree of sensitization that a patient has undergone when assessing them for a potential graft.
You can test their serum against a panel of individuals from the population, the results are expressed as the percentage of positive reactions against the panel
What is acute graft rejection ?
Acute graft rejection is mediated by effector T cells that respond to HLA differences between the donor and the recipient
What is acute rejection a result of ?
Newly formed acquired immune response that is initiated against alloantigens following the graft procedure.
What does MHC genotype have to do with successful grafting ?
Mice that have transplanted tissues with identical MHC expression have perfect grafts. Grafts between mice of different MHC haplotypes will always be rejected. If the mice have different MHC haplotypes
Do tissue rejections mount a second offense?
Yes the rejection will be much faster when the mouse has already rejected tissue from one allotype.
What are the three most important HLA haplotype genes involved in organ transplantation ?
HLA-A, HLA-B, and HLA-Dr
What are the two tissues that HLA matching is not as important ?
Liver and the Cornea
What is HLA matching not as big of a deal for the cornea ?
It is not vascularized
What is required for Liver transplantation ?
HLA antigen is not a big deal for the liver, it is refractory to acute rejection. ABO blood group is
Describe Graft Versus Host Disease
It is mediated by mature T cells of the Donor that were in the grafted tissue. If any of these T cells are specific for the recipients "Self" antigens CTL's will attack the recipients cells.
What kind of transplant is GVHD most prevalent in ?
Why do you not have GVHD in solid organ transplants ?
A rejection of a solid organ transplant is mediated by the alloantigens to the grafted tissue only.
What cells in the recipient can GVHD attack ?
GVH disease can result in alloreactions against almost any tissue in the recipients body
What are the primary tissues affected in graft versus host disease ?
Skin, Intestines, and Liver