Exam 2- Chapter 5 Flashcards by Amanda Pearman

TCR

A membrane-bound glycoprotein that has 2 polypeptide chains- TCR alpha and TCR Beta

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TCR regions (2)

Variable (V) and constant (C)

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T-Cell Receptor diversity is generated similar to:

Immunoglobulin but without later hypermutation or switching

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What type of receptor is TCR?

Simple

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TCR gene regulation occurs where?

In the thymus

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When TCR rearrangement does not operate correctly, what is the result?

Severe combined immunodeficiency disease (SCID)

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TCR expressed on the surface has:

Helper membrane proteins- (CD3 complex)

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What assist the TCR with intercellular signaling?

CD3 proteins and an additional zeta chain

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T cells are either ______ or _____

Alpha:beta T cells

Or Gamma:delta T cells

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Second class TCR

TCR game:delta

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T cells that are more complex and not understood

Gamma:delta T cells

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TCR Anitgen presentation

Display of peptide antigens on the cell surface to be recognized by TCR- a person eating at a diner

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Production of peptide antigens within human cells

Antigen processing

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Antigen processing is generated by:

degrading pathogens

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Cells involved in antigen processing

Macrophages and dendritic cells— these are the chefs

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What is the antigen presentation on?

Major histocompatibility complex molecules (MHC) (The silver platter)

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MHC class that presents antigens from intracellular pathogens, like viruses

MHC Class 1

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MHC Class 1- what breaks down the virus?

Proteases es

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In MHC class 1s, where are the degraded peptides delivered to?

To the ER

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________ bind to MHC Class 1 for presentation

Peptides

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MHC class 1 is present where?

All cells except RBC and is limited on neurons

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Why is MHC class 1 only limited on neurons?

Class 1 presentations result in apoptosis. We do not want our nerve cells to die

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Why are there no MHC class 1 in RBC?

RBC have such a short life span, there really is no point

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MHC class that presents antigens from extracellular pathogens, like phagocytosed bacteria

MHC class II

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What is broken down in MHC class II receptors?

Phagocytosed pathogens

Where to peptides bind to MHC Class II?

In endosomal vesicles

Where are MHC class II presented?

Only on phagocytic cells

MHC class I molecules are recognized by what?

Cytotoxic T cells (expressing CD8 molecules)

What do MHC class I molecules defend against?

Intracellular infections

MHC class II molecules are recognized by:

Helper T cells (expressing CD4 molecules)

What do MHC class II molecules defend against?

Extracellular infections

CD8 cells

Cytotoxic T cells

What do CD8 cells do?

Kill cells that are infected with an intracellular virus, bacteria, or other pathogen

What do CD4 cells do

Activate macrophages to increase phagocytosis and activate B cells to produce effector antibodies

Co-receptors assist with:

Binding of T cell to target cell

Structure of MHC class I

Has 3 alphas and 1 beta microglobulin

Structure of MHC class II

2 betas and 2 alphas

What does CD8 bind to?

The Alpha 3 domain of MHC class I

What does CD4 bind to?

The beta 2 domain of MHC class II

What happens when MHC binding occurs?

There are extra co-receptors to make sure it is binding to the right place.

What restricts what peptides are presented?

Noncovalent binding to peptides

MHC binding specificity

It will bind to many peptides- very promiscuous

Incorrectly made proteins in the cytoplasm are:

Degrades by intracellular proteases

What happens when viruses invade a cell?

They are degraded by intracellular proteases in the cytosol

In a healthy cell, MHC class I will present:

Only host proteins

In a viral infected cell, MHC Class I will present:

Both host and viral proteins

For MHC class II, what are the pathogens brought into the cell by?

Phagocytic vesicles

What happens within phagocytic vesicles

Pathogens are degrades and then bind to MHC class II

When an extracellular infection is occurring, MHC class II presents:

Pathogenic peptides

MHC class I proteins are broken down by:

Proteasomes in the cytosol

Large barrel-shaped complexes that recognize proteins intended for degradation

Proteasomes

What varies peptide production for better fit to MHC class I?

Immunoproteosome

Antigenic peptides are transported into the ________ through:

ER Through a transporter associated with antigen processing (TAP)

Where are the MHC class I molecules synthesized?

In the ER

Chaperones that fold and load MHC class I

Calnexin | Tapas in

What does Calnexin do?

Folds MHC class I molecules

What does Tapasin do?

Loads MHC class I with non-self peptides

MHC class II peptides- what breaks down the contents of phagosomes?

Lysosomes

Vesicles with peptides fuse with:

Vesicles containing the MHC class II molecules

Upon fusion between peptides and MHC class II molecules, what happens?

Peptides are loaded into the MHC class II molecules

What blocks the binding site of MHC class II molecules?

Invariant chain

What happens to the invariant chain?

It is cleaved leaving the CLIP in the groove

What molecule pulls the CLIP out of the groove so the peptide can bind?

HLA-DM

How often can peptides be transferred from MHC class II to class I

Rarely

Transfer of MHC class II to class I

Cross-presentation

MHC molecules were Originally recognized in :

The rejection of organ transplant

MHC molecules are also called

Human leukocyte antigen complex (HLA complex)

No MHC gene rearrangement during:

Processing

What are considered for transplants?

Compatibility

What occurs between MHC and TCR?

Twofold recognition