Immunology T3

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  • Created by: Kavita :)
  • Created on: 17-02-15 14:07
What are the two major intracellular compartments seperated by membranes?
Cytosol & Vesicular system
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Cytosolic pathogens, Intravesicular pathoges, Extracellular pathogens + toxins, where are these 3 degraded? what MHC molecules to they bind and present to? What is the Effect
1) CP - degraded in CYTOSOL, MHC I present to CD8+ cell death 2) IP - degraded in ENDOCYTIC VESICALS (low pH), MHC II present to CD4+, activation to kill intravesicular bacteria 3) EP degraded in ENDOCYTIC VESICALS, activation of B cells secrete Ig
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What do the TAP complexes do?
Actively tansport peptides that bind to MHC I from cytosol to ER
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Where are peptides generated?
1) Can be from pathogens or degraded self-proteins 2) Generated in cytosol by proteolytic digestion in proteosome
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Where are newely synthesized MHC I retained?
In the ER until they bind peptide
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Draw the process of MHC I in ER when a peptide binds (4 stages)
-
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What do viruses produce that interfere with antigen presentation by MHC I?
Immunovasins
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Where are peptides presented by MHC II molecules generated?
Acidified endocytic vesicals. Acidification of vesicals activates proteases to degrade antigen into peptide fragments. Vesicals containing fragments fuse with vesicals containing MHC II molecules.
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What does the invariant chain do? How?
It directs newley synthesized MHC II molecules to acidified vesicals. Invarient chain binds to groove of MHC II - cleaved to shorter peptide CLIP which blocks peptide binding.
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What happens to CLIP when vesical is directed?
HLA-DM binds to MHC II releasing CLIP allowing other peptides to bind. MHC II travels to cell surface
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What is autophagy?
Some damaged organelles + cytosolic proteins are delieved into endosomes by autophagosomes for proteolytic breakdown
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How does the immune system ensure CD8 response to all viruses, even if they fail to infect APCs?
partialy degraded antigenic material in endosomal pathway can be loaded into the Class I pathway by TRANSLOCATION INTO CYTOSOL. MHC II can present cytosolic proteins - Autophagy.
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What is cross-presentation?
The ability of APCs to take up, process & present extracellular antigens with MHC I to CD8 T cells. Permits presentation of exogenous antigens which are normally presented by MHC II.
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What does polymorphism and polygeny contribute to?
Diversity of MHC molecules and all are expressed co-dominantly.
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How many genes encode MHC I molecules?
3 Genes (A, B, C) high amount of allelic variation
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What is a haplotype?
A full array of alleles for MHC molecules on chromosome 6. All genes expressed co-dominatly. 6 classes of MHC I expressed
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How many pairs of genes are coding for MHC II?
3 paids (DP, DQ, DR) all with A, B each
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What does polygenic mean?
Different genes from both parents, all are expressed and variation between alleles due to polymorphism - huge diversity of MHC molecules that can be expressed.
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Which part of MHC II has most variability?
B chain
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What is MHC restriction?
TCR is restricted to only recognise self-MHC molecule - recognition
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Where are the genes for TAP 1&2, Tapasin & Proteosome subunit located?
MHC Class II locus
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What is a super-antigen?
They do not bind to MHC groove but outside of the MHC molecule and TCR. They do not stimulate one close of T cell, but can stimulate ALL T cells! Non-specific binding. Toxic Shock (TSS - Staph Aureus)
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Card 2

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Cytosolic pathogens, Intravesicular pathoges, Extracellular pathogens + toxins, where are these 3 degraded? what MHC molecules to they bind and present to? What is the Effect

Back

1) CP - degraded in CYTOSOL, MHC I present to CD8+ cell death 2) IP - degraded in ENDOCYTIC VESICALS (low pH), MHC II present to CD4+, activation to kill intravesicular bacteria 3) EP degraded in ENDOCYTIC VESICALS, activation of B cells secrete Ig

Card 3

Front

What do the TAP complexes do?

Back

Preview of the front of card 3

Card 4

Front

Where are peptides generated?

Back

Preview of the front of card 4

Card 5

Front

Where are newely synthesized MHC I retained?

Back

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