L03 Flashcards
T cells leave the bone marrow before B cells. where is T cell gene rearrangement take place
thymus
what process is not involved in generating the diversity of TCR
SMH
what chromosome encodes for TCR alpha
14
what chromosome encodes for TCR beta
7
what chromosome encodes for TCR gamma
7
what chromosome encodes for TCR delta
14
gene rearrangement happens to MHC molecules
False
where is MHC molecule (HLA) in humans located
chromosome 6
what cells express MHC class 2
B cells, macrophages, dendritic cells (antigen presenting cells, APC)
T cells express both MHC classes
true
how many different MHC molecules can a person have
12 if they are heterozygous for all 6 MHC loci
what are the 3 MHC class 1 molecules
HLA-A, HLA-B and HLA-C
what are the 3 MHC class 2 molecules
HLA-DP, HLA-DQ and HLA-DR
Location of polymorphic residues within MHC structure is random
false
where is the most variable region of the MHC molecule
peptide binding domain
what might MHC polymorphism lead to
increases risk of immune-mediated disease e.g. autoimmune diseases (i.e. increases likelihood of presenting self Ags.)
reduces pool of available donor organs for transplantation
(as MHC alleles on donor organ should match those of the
recipient for best outcome)
what peptides are presented on MHC class 1
peptides derived from protein Ags synthesized inside a cell (endogenous Ag e.g. from an intracellular pathogen such as a virus)
what peptides are presented by MHC 2
peptides derived from protein Ags taken up from the outside of the cell (exogenous Ag e.g. from an extracellular pathogen such as a bacterium/fungus)
peptides are processed before presenting in endogenous and exogenous Ag
True
what are the steps of presenting peptides on MHC 1
1) Ag. (e.g. viral protein) synthesized in cytoplasm
2) protein cleaved to peptides by proteasome
3) peptides transported to endoplasmic reticulum by TAP transporter
4) peptides bind to MHC class I molecules
5) MHC-I/peptide complex then transported to cell surface
what is the proteosome function
cytoplasmic protein turnover
proteasomes in cells receiving inflammatory cytokines signals are modified to produce altered peptides
True
what is TAP
TAP is a component of a multi-protein assembly, the peptide loading complex
also includes tapasin and calreticulin
what does TAP do
delivers a peptide that binds to the MHC 1 and completes its folding
the fully folded MHC 1 is released from the TAP complex and exported
TAP is a dimer with a hole in the middle
True
what are the steps of presenting peptides on MHC 2
1) Ag. (e.g. bacteria) endocytosed into intracellular vesicles inside the cell
2) protein cleaved to peptides by acid proteases in vesicles
3) vesicles fuse with vesicles containing MHC class II molecules
4) peptides bind MHC class II molecules
5) MHC-II/peptide complex then transported inside vesicles to cell surface
what does MHC class II molecules binding to invariant chain in the ER
this prevents peptides binding in the groove
what are the steps of unblocking MHC 2
invariant chain forms a complex with MHC 2 blocking binding of peptides and misfolding the protein
it is cleaved in an acidified endosome, leaving a short peptide fragment, CLIP, still bound to MHC 2
endocytosed Ag are degraded to peptides in endosome but CLIP is still blocking the binding of the peptides with MHC 2
HLA-DM binds to the MHC 2, releasing CLIP and allowing other peptides to bind and MHC 2 then travels to the surface.
what happens to MHC molecules in healthy cells
MHC molecules present self proteins
Accessory molecules involved in antigen processing and presentation are also encoded within the MHC (TAP and LMP (class I pathway ) HLA-DM (class II pathway ))
True
which cells recognize and kill cells infected by viruses
cytotoxic CD8 T cells
What do cells that express MHC 2 (APC) do
take up and present extracellular Ag to activate helper CD4+ T cells
some other cell types can express MHC class II under certain conditions allowing them to be recognized by helper CD4+ T cells.
True
