MHC Structure and function Flashcards
(28 cards)
HLA or human leukocyte antigen refers to which structures?
MHC molecules
Name the two sets of polymorphic genes found on MHC loci.
MHC I
MHC II
Describe the structure of an MHC I protein including the bond between the chains.
3 alpha chains and 1 beta-2 microglobulin
alpha 1 and alpha 2 form the binding cleft/groove
beta-2 microglobulin and alpha 3 form
the alpha 3 binds the CD8 coreceptor (NOT CD4!!!)
The b-2 microglobulin is bound noncovalently to the alpha chain
The upper 2 subunits are polymorphic
the lower 2 subunits are not polymorphic
General structure of an MHC molecule
4 subunits (may consist entirely of alpha chains or include a beta-2 microglobulin chain)
The upper 2 subunits form the binding cleft/groove
The binding cleft is made of amino acids
The floor of the binding cleft binds the antigen
The walls of the binding cleft will bind to the coreceptor
the lower subunits will bind the T cell coreceptor
What are the reasons for someone having high levels of Antibodies? [3]
Multiparous (given birth multiple times)
Multiple transfusions
Multiple grafts/transplants
What are the properties of MHC genes? [4]
- Highly polymorphic
- Polygenic (different non-allelic genes involved)
- Co-dominantly expressed
- Have pleiotropic functions (produce more than one effect)
How many alleles of MHC class I loci do you get from each parent?
3
HLA-A
HLA-B
HLA-C
Define MHC haplotype
set of MHC alleles present on each chromosome
MHC proteins can only bind peptides in which location?
Inside the cell during their synthesis and transport
What is one necessary condition for MHC molecules to be expressed on the cell surface?
they must already have a bound peptide
Can MHC molecules discriminate between self and non-self?
No
If MHC molecules are constantly displaying self-antigens, why does autoimmunity not occur?
because the t lymphocytes reactive to self antigens are destroyed or inactivated
What is the purpose of segregating antigen processing pathways? Which pathway occurs in which compartment?
The purpose is to allow sampling of peptides from both intracellular and extracellular compartments. The class I MHC pathway is for intracellular components in the cytosol. The class II MHC pathway is for exracellular proteins.
which DNA typing method is used for HLA typing?
southern blot - using electrophoresis separated DNA fragments, filtering them via a filter membrane, and detecting them via probe hybridization
which serological typing method was used for HLA typing?
MLR (mixed lymphocyte reaction)
MHC I molecules are expressed in all nucleated cells except?
RBCs
Trophoblasts of placenta
On which cell types do MHC II molecules tend to expressed?
Macrophages
Dendritic cells
B lymphocytes
(basically APCs)
The MHC III gene encodes for which molecules?
Complement
Heat-shock proteins
Cytokines
What are the two parallel nomenclatures used in identifying MHC alleles?
Serological (based on Ab’s) - lower resolution
Parallel (based on DNA testing) - uses * to identify specific alleles so has higher resolution
Which kind of antigens are recognized by T lymphocytes versus B lymphocytes?
T lymphocytes only recognize protein antigens
B lymphocytes can recognize in addition polysaccharides, lipids, and nucleic acids
Define MHC restriction
A property of T lymphocytes that refers to their limited capability to only recognize MHC-bound antigens.
Name the most specialized and efficient APC.
Dendritic cells
How would a rare lymphocyte for a microbial agent find that microbe, considering that microbes can enter anywhere in the body?
The microbe is taken up by a dendritic cell and transported to a lymphoid organ through which lymphocytes are constantly recirculating
the two major types of dendritic cells as well as their locations.
classical (in tissues and lymphoid organs)and plasmacytoid (in blood and tissues)
