Term
| Basic structure of TCR and MHC molecules |
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Definition
TCR resembles a membrane-bound Fab; a heterodimer composed of an alpha and beta chain (or gamma and delta)
-EC portion has two Ig-like domains: one V-like, one C-like
-a member of the Ig superfamily
-both alpha & beta chains span the cell membrane, have short cytoplasmic tails
-heterodimer is associated with CD3 complex (gamma, delta, epsilon), and zeta. This complex does the signaling
-the cytoplasmic domains of CD3 proteins contain ITAMs, allow them to associate with protein tyr K (PTK)
-CD3 also req'd for expression of TCR on cell surface
MHC complex: region encoding MHC molec & other pr involved in Ag processing & presentation; causes T cells to reject transplants
-human MHC is called human leukocyte antigen (HLA); murine MHC is called histocompatibility-2 |
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Term
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Definition
4000 kb, on csome 6
class II region contains TAP1 & TAP2 genes (transporters in antigen processing) & LMP genes that encode proteosome subunits
-products of TAP1/2 --> protein pump, transports peptides from cytosol into ER where they can associate with MHCI H chains
Class III region separates I & II, contains complement genes
gene for beta-2 microglobulin *is not* on MHC (it's on csome 15) |
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Term
| how polymorphism affects binding & presentation of peptide antigens to T cells |
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Definition
Polymorphism = variation at a single genetic locus and its product within a species
most of the polymorphic residues are located at the alpha1 & alpha2 domains of class I, and mainly the beta1 domain of class II, the domains that form the peptide binding cleft
affects Ag recognition indirectly by controlling peptide binding |
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Term
| Understand the complex of peptide antigen and MHC molecule recognized by T cell receptor (TCR) |
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Definition
| T cells recognize antigen ONLY in the presence of peptide bound to MHC on cell surface |
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Term
| Antigen processing and presentation |
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Definition
-antigen processing: the breakdown of pathogen derived proteins into peptide fragments
-Ag presentation: assembly of peptides with MHC and display of these complexes on cell surface |
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Term
| MHC-restriction of T cells |
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Definition
The recognition of an Ag by T cells is specific for the Ag as well as the MHC molecule that presents the Ag
-e.g. cytotoxic T cells isolated from a virally infected animal won't kill cells infected by the same virus from another animal of a different MHC haplotype |
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Term
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Definition
transport peptides from cytosol into ER
essential in MHC class I peptide loading |
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Term
| MHC class I & II isotypes |
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Definition
I: HLA-A, HLA-B, HLA-C, HLA-E, HLA-F, HLA-G
-have an alpha or heavy chain and a non-MHC-encoded beta (beta2-microglobulin) chain
-alpha chain folds into alpha1, alpha2, alpha3. a1 & a2 form peptide binding cleft, can accommodate peptides of 9-11 AA
-A, B, C are "classical"
II: HLA-DP, HLA-DQ, HLA-DR, HLA-DM, HLA-DO
-are heterodimers of alpha and beta chains
-alpha1 & beta1 domains form peptide bonding region, can accommodate peptides of 10-30 AA
-DP, DQ, DR are "classical" |
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Term
Where are MHCI expressed?
On what cells are MHCII expressed? |
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Definition
B/c MHC is polymorphic most ppl are heterozygous at each locus
Class I molecules are expressed at all nucleated cells
Class II are normally only expressed on APC (B cells, macrophages, dendritic cells) |
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