L21, L25, L27- Antigen Presentation, Recognition Flashcards
B-cells recognize (1) type molecules in (2) form
1- proteins (mainly), polysaccharides, lipids, nucleic acids
2- soluble form, or cell surface-associated antigen
T cells recognize (1) type molecules in (2) forms
1- peptide fragments
2- presented on specialized molecules (MHCs via APCs)
antigens are usually presented to T-cells via (1) on (2) cells after its migration/maturation in (3) via (4) molecules and (5) signaling
1- MHC-II receptors 2- dendritic cells 3- lymph nodes, paracortical area 4- chemokines 5- TLR-signaling
the most important APC is (1) and usually presents its antigen in the (2) area of (3)
1- dendritic cells
2- paracortical area
3- lymph nodes
list the 3 signals that stimulate T-cells via antigen signaling
1) antigen presentation: MHC/peptide (dendritic cell) recognized by T-cell receptor
2) co-stimulatory signal: CD28 (T-cell) recognized by CD8o/CD86 (dendritic cell)
3) CK secretion: CKs (dendritic cells) recognized by T-cells
MHC genes are found on the (1) cluster of genes on Chromosome (2)
1- HLA (human leukocyte antigen)
2- chr. 6
list the MHC-I gene classes
HLA-A, HLA-B, HLA-C
list the MHC-II gene classes
DP(αβ), DQ(αβ), DR(αβ)
MHC-I receptors are found on (1) cells
MHC-II receptors are found on (2) cells
1- all nucleated cell
2- APCs
MHCs genes are expressed in a _______ fashion
co-dominant expression (both parental alleles are expressed)
describe the components of MHC-I
α-chain (α1, α2, α3): transmembrane, encoded by A/B/C regions of MHC complex
β2-microglobulin: encoded by highly conserved gene (different chromosome)
Of the MHC-I complex:
- (1) is the highly polymorphic polypeptide binding region
- (2) binds to CD8 of T(c) cells
- peptides that are (3) peptides long are recognized (antigen)
- antigens presented are processed (endo/exo)-genously
1- α1/α2 subunits (target cell) binds to T cell receptor
2- α3
3- 8-10 AAs
4- endogenously
describe the components of MHC-II
Heterodimeric protein (Ig superfamily)
- α1, α2: transmembrane
- β1, β2: transmembrane
Of the MHC-II complex:
- (1) is the highly polymorphic polypeptide binding region
- (2) binds to CD4 of T(h) cells
- peptides that are (3) peptides long are recognized (antigen)
- antigens presented are processed (endo/exo)-genously
1- α1/β1 (α2 is highly conserved region)
2- β2
3- 13-25 AAs
4- exogenously (via Ig)
list the APCs
dendritic cells, macrophages, B-cells
MHC-I receptors are recognized by (1) on (2) cells and will result in the release of (3) and (4) with the following functions, (5) and (6) respectively
1- CD8
2- T(c) cells
3/5- perforins: forms pores in cell membrane
4/6- granzymes: protein breakdown + cell lysing
MHC-II receptors are recognized by (1) on (2) cells and will result in the release of CKs resulting in (3) which will produce different CKs activating (4)
1- CD4
2- T(h) cells
3- T-cell clones
4- B-cells, T(c) cells
list the two antigen presenting pathways, their alternate names, and their MHC/T-cell association
Cytosolic, endogenous, non-lysosomal pathway (produced in cell): MHC-I, CD8 T(c) cells
Endocytic, exogenous, lysosomal pathway (taken via endocytosis): MHC-II, CD4 T(h) cells
In the cytosolic antigen presenting pathway, infected proteins are marked with (1) to be degraded by (2). The resulting peptides will bind to (3).
1- ubiquitin
2- proteosome
3- MHC-I
proteosome components in cytosolic antigen presenting pathway are activated via….
INF-γ (inc number of proteosome components)
Peptides from the proteosome in the Cytosolic pathway enter the ER via (1) and bind to (2). Once loaded on, (2) will signal for (3) or (4) via the Golgi apparatus.
1- TAP1/TAP2
2- MHC-I
3- exportation to cell surface
4- sent to lysosome for degradation (usually if no antigen binds)
list the targets of immunoevasins that interfere with antigen presentation via MHC-I
(virus blocks MHC-I presentation to T(c) cells)
- inhibit peptide transport
- inhibit peptide loading
- cause MHC-I degradation
(1) virus blocks it viral peptide from transport into ER via (2) and leads to (3)
1- HSV
2- TAP1/TAP2
3- MHC-I degradation via lysosome
(1) virus retains MHC-I in the ER, leading to (2)
1- adenoviral protein
2- MHC-I degradation via lysosome