antigen recognition by T lymphocytes Flashcards
do t cells under go somatic hypermutation? and why would you want it to happen or not.
No, you do not want t-cells to incorporate random mutations into their ability to recognize self
qualities of T cells compared to B cells
- have different MHCs and only have peptides
- has surface expression of receptor which doubles as effector molecule
- no somatic hypermutation
- no constant region switching
- interacts with other cells
- clonal populations
Do T cells have heavy and light chains?
No, they have alpha and beta chains
structure of a T cell
1 alpha chain, 1 beta chain, 6 hypervariable loops (3 on each arm), single binding site with multipoint attachment
is T cell receptor diversity is generated by gene rearrangement
Yes
where does TCR gene recombination take place
in the thymus
how to fix severe combined immunodeficiency and Omenn syndrome
bone marrow transplant
what genes are key elements in the origin of adaptive immunity
RAG genes
what chromosome is the RAG genes on
11
does expression of the t cell receptor on the cell surface requires association with additional protein
yes, it is required for transport from the ER, signal transduction
what does the absence of epsilon and delta lead to
immunodeficiency
how specific do the alpha and beta t cells need peptides to be given to them
need to be given directly
how specific do the gamma and delta t cells need peptides to be given to them
they do not care how the peptide is given to them
what percent of T cells are in circulation
1-5%
what causes T cell receptors to recognize MHC molecules
peptide antigens
MHC class 1 structure
has a beta 2 macroglobulin attached to the rest of the protein structure
MHC class 2 structure
symmetrical structure
what do MHC class 1 present to
CD8+ cells (killer t cells)
what do MHC class 2 molecules present to
CD4+ (helper t cells)
which cells are exploited by HIV
CD4 and CD8 glycoproteins
what do CD8 t cells do when recognizing viral antigens
find the MHC class 1 presenting the viral protein, and kill the infected epithelial cell
what do CD4 t cells do when recognizing viral antigens
when the MHC class 2 presents the viral protein it binds to it, releases cytokines in order to activate the macrophage which will then kill the cell.
which MHC cell has a dual chain binding groove
MHC 2
which cellular compartment does MHC class 1 function
intracellular in the cytosol and ER
which cellular compartment does MHC class 2 function
extracellular, in the endosomes and lysosomes
MHC class 1 binding process
antigen processing to peptides in proteasome, peptide transport into endoplasmic reticulum (ER), then peptide binding by MHC class 1, and then MHC class 1 presents the peptide at cell surface
MHC class 2 binding process
peptide production in phagolysosome, peptide binding by MHC class 2, MHC class 2 presents peptide at cell surface
is peptide processing and presentation in MHC 1 molecules a continuous process?
yes, it is not a product of infection
MHC class 2 molecules are expressed by what cells
professional antigen presenting cells
what cells do not express MHC class 1 or 2 molecules
erythrocytes (RBCs)
where are peptides presented by MHC class 2 molecules generated in
acidified intracellular vesicles
which pathogens exploit the MHC class 2 pathway in order to hide from CD8 T cells
leprosy and tuberculosis
what does the invariant chain do
blocks binding of peptides to MHC class 2 molecules in the ER until the time is right. when time is right DM facilitates the release of CLIP to allow peptide binding
what does cross-presentation do
allows extracellular antigens to be presented by MHC class 1 if the virus has infected an extracellular component.
which cells use MHC class 2 molecules
macrophages and dendritic cells
what region of DNA is responsible for transplant rejection by T cells in unrelated patients
MHC complex on chromosome 6
are HLAs the human version of MHCs
yes
does HLA class 2 have more allotypes than class 1?
yes
do HLA class 1 and 2 genes occupy different regions of the HLA complex
yes
do MHC polymorphisms affect the binding and presentation of peptide antigens to T cells
yes
does heterozygosity for MHC alleles confer a selective advantage
yes
