Chp 5 Flashcards by Jacquelynn Gasper

Five ways TCR are similar to BCR

TCR has similar structure to FAB on BCR

Both generated through somatic recomb

TCR - a:b chains BCR- heavy light
chains

Junctional diversity

Both require CD3

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Difference b/w TCR an BCR

TCR has 1 antigen binding site
BCR has 2

TCR never se created

TCR generated in Thymus BCR-BM

TCR no effector function - only surface receptor

BCR - isotype- effector function

TcR no hypermutation

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TCR

A resembles The light chains

Both contain VJ segments

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TCR alpha is located on what chromosome

On chrom 14

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TCR B

Resembles heavy chain on imm

On chrom 7

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TCR

Not undergo isotype switching because they are not made is secreted for and their C region don’t contribute to effector function

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CD3 and Zeta chain roles

On surface of the cell is to transducer signals to the interior of the TC

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Conseque of SCID caused by defect in

Defect of RAG 1 or 2

lacking somatic recombination in TCR

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Which of the following removes CLIP

HLA-DM

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Describe MHC I

Heterodimer
One a chain
B2 -micro globulin 
A chain=1,2,3
Cytoplasmic tail

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B2 microgloubulin

On mHC I

Single domain protein non cov, associated with the alpha chain

Provides support and stability

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MHC I : humans

HLA- a,b,c

Polymorphic

Gut uptake of imm
Regulation of FR
Reg of NK

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What chain in MHC I has greater diversity?

A- has greater diversity

B- MHC II

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MHC II is made up of …

Made of a:b chain
Heterodimers
B chain contains b1,2
Transmembrane 
Cytoplasmic tail

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MHC II humans

3 polymorphic class molecules

HLA- DP, DQ, DR

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MHC II

B2 binds to the TC co receptor Cd4

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Antigen processing

The intercellular breakdown of pathogen derive proteins into peptide frag that bind to mHC

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Antigen presentation

The assembly of peptides with MHC displayed on surface of APC

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TC activation must be bound on what?

TCR can bind only to peptide

Antigen must be bound on surface of APC

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Endogenous Antigen processing pathway

Proteins in the cytoskeleton are broken into small fragments in the protea some
Transported in ER using TAP
Peptides that bind to MHC I delivered to Er
A chain bound to chaperone calnexin until B2 m binds
Then are bound by the chaperones calrecticulin and tapasin until peptide binds
Tapasin binds to tap-1 positioning the MHC near the peptide source
peptide delivered by TAP binds to heavy chain forming the mature MHC I molecule
MHC dissociates from the peptide loading complex and export progress to the Golgi then to be transported to cell surface

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What happens if RAG is lacked?

Adaptive immunity would be compromised

SCID
Non functional TC & BC

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Def in CD3?

TC have low number of of receptors that do not signal effectively

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CD 3 def

Immunodeficiency
Absent of TC
Non func BC
Early death die to ScId

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G:d is ass with what?

The gut mucosa
Do not require antigen processing and mhC molecules
Does not have cD8 or CD4

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TCR is what?

Surface receptor - no effector fun

TCR only recognizes antigens in what form?

Of peptides bound to MHC

Cd8 binds to what?

Alpha 3

Cd4 binds to what?

Beta 2

MHC I

Greater restriction 8-10 AA (short) Hydrophobic/basic at c-term

MHC II

More leanent Not as restrictive Long 13-25 AA

Calnexin is...

Lectin chaperone Holds MHC I heavy chain Until B2m loaded

Calrecticulin

Lectin chaperone, quality control

ERp57

Promotes folding of heavy chain

Tapasin

Transmembrane protein that tethers empty class I molecules to TAP

PDI

Protein disulfide isomerase | Catalysts disulfide bond formation

ERAP

Removed aa of peptide that is too long Improves binding affinity

What happens if def in TAP?

Tap is the channel in the ER so if def then no peptides enter the ER So very poor cd8 response Chronic respiratory

MHC I

Intracellular envir

MHC II

extra cell pathogens

MhC II is ass with what chain?

Invariant chain

What does the invariant chain become?

Clip

What is the function of invariant chain?

Prevent MHC II from binding peptides in ER Delivers MHC II to vesicles Leaves clip HLA-DM

What forms the central part of binding site?

CDR3- most variable

What cells are MHC I expressed on?

All cells

Cross presentation

Antigens of extra cellular origin can be presented by MHC I

What char is common to both TCR and Ig?

Somatic recom of VDJ segments is responsible for the diversity of antigen binding sites

TCR a resembles...

Light locus on Ig

TCR b chain resembles ...

Ig heavy locus

MHC complex closely linked genes on what chrom...?

Chrom 6

Polgeny

Result of expression

Polymorphism

Existence within pop of many alt forms of MHC I & II Allotypes

Polgeny

Isotypes

HLA genes of MHC I

``` HLA A B C E F G ```

HLA-E

Ligand for Nk

HLA- F

Unknown func

HLA-G

Ligand for NK

HLA E & G

HLA genes for MHC II?

``` HLA DM DQ DP DR ```

What MHC has the greatest diversity ?

MHC 1

What is the function of g:d?

First line of defense against invading pathogens

TCR diversity is generated by...?

Gene rearrangement

What are there more forms of HLA polymorphism ? MHC I or II?

Many more forms of MHC I

Haplotype is what?

MHC genes are inherited as a group one from each parent 6M/ 6D

A heterozygous human inherits what ?

One maternal one paternal Ea contain : ``` 3 class I (abc) 3 class II (DP,DQ,DR) ```

A normal tissue type will involved how many HLA antigens ?

A cross over results in what?

New haplotypes

Why so many MHC alleles?

MHC most polymorphic genes known Different pathogens generate different antigenic fragments

Other proteins involved in antigen processing and presentation ?

Tapasin | Immunoprotrasome LMP2, LMP7

HLA class I don't involve....?

Antigen processing and presentation

HLA I functions?

Gut uptake Reg of Fe Ref of NK

MHC I is more evolutionary

More older

HLA region III has what ?

Components of complement sys | Cytokines (TNF)

What MHC II polymorphism not vary?

HLA-DR

Is B2 microgloubulin polymorphic?

TCR has what...?

Restriction responds to peptide presented by one MHC

HLA diseases

``` Rheum arthritisis Type I diabetes Celiac Graves MS Breast cancer ```

Wht are the types of MHC haplotypes?

Balancing selection | Directional selection

How are MHC alleles generated by?

Interallelic intercom version or gene conversion

Why is a transplant rejected?

The alloreactivity of TC The MHC they were not selected for in the thymus and why the TC sees it as a foreign MHC

TC respond strongly to what..

Allografts

Cd4 are alloreactivity to what ?

Class II alloantigens

Cd8 alloreactivity to

class I alloantigens

Is MHC highly polymorphic?

Yes seen by alloreactivity TC