Major Histocompatibility Complex (MHC) and Antigen Processing and Presentation to αβ T Cells and Transplantation Flashcards
What molecules present antigen to the adaptive immune system?
MHC I and MHC II
What molecules does the adaptive immune system use to recognize antigens?
B-cell receptor and T-cell receptor
What is the immunoglobulin superfamily?
any molecule that has a basic domain structure; similar to the structure of antibody (110 amino acid domains)
What are examples of molecules in the immunoglobulin superfamily?
CD4, bcr, trcm, cks
What is the structure of MHC I?
long alpha chain, one transmembrane portion and a beta 2 microglobulin chain
Where is MHC I located?
on all nucleated cells
What T cell binds to MHC I?
CD8 - cytotoxic T cells
Is MHC I endogenous or exogenous?
endogenous
How many AA long is MHC I?
9
Where is MHC II located?
on all antigen presenting cells; dendritic, macrophage, and memory b cells
What is the structure of MHC II?
An alpha and beta chain both containing a transmembrane portion, and a peptide binding region
What T cell binds to MHC II?
CD4 - t helper cell
Is MHC II endogenous or exogenous?
exogenous
What type of vaccine would follow the exogenous pathway?
killed vaccines
What are the steps of the exogenous pathway (4)?
- Dendritic cell breaks it up into peptides in a vesicle
- Dendritic cell is creating an MHC 2 molecules with an invarient chain blocking the groove
- When the vescicle fuses with a lysosome, the invarient chain is removed which allows peptides to be bound to the MHC 2 molecule
- It then goes to the cell membrane to present itself to a CD4 cell (t-helper cell)
What type of vaccine would follow the endogenous pathway?
live vaccines
Where must the protein be located in the endogenous pathway?
in the cytoplasm
What are the steps of the endogenous pathway?
- Protein is tagged with ubiquitin - for processing by a proteosome
- It then goes into the lumen
- The peptides are moved in to the MHC I pathway and then is presented to the membrane and the CD8 cell
What is a proteosome?
a hollow cylinder that unfolds the protein and chops it into peptides
What is the difference between the antigens presented in the endogenous pathway and the exogenous pathway?
the antigens presented in the endogenous pathway must be in the cytoplasm, whereas they are on the outside in the exogenous pathway
How does ISCOM work?
It is able to carry proteins into the cytosol so that the protein can be presented on MHC I to stimulate a CD8 t cell response
What are the benefits of using immune stimulatory complexes to deliver an inactivated antigen?
killed vaccines or purified proteins and stimulate CD8 cells by using this otherwise they are taken up via phagocytosis
How many different MHC I molecules can an individual have?
6 molecules
How many different MHC II molecules can an individual have?
8-10 molecules
What is the MHC heterozygote advantage?
animals with 6 different MHC molecules can bind and present a greater variety of antigen where as homozygous animals with only 3 do not have a large variety of antigen
What is the role of MHC in tissue transplantation?
T cells recognize peptides in the MHC type, if they are not all the same they are considered a foreign MHC which can lead to rejection and death of cells
