Ch 3 Day 2 (I)

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Questions and Answers

Which cellular structure is responsible for proteolytically generating peptide fragments of proteins displayed by class II MHC molecules?

Cytosol

Late endosomes and lysosomes (correct)

Proteasomes

Macrophages

What type of T cell is activated by the proteasomal processing pathway?

B cells

Macrophages

CD4+ T lymphocytes

CD8+ T lymphocytes (correct)

From where are the proteins found in late endosomes and lysosomes largely derived?

Extracellular environment (correct)

Mitochondria

Endoplasmic reticulum

Cytosol

Which pathway ensures that CD4+ T lymphocytes will be able to recognize antigens from microbes originally present outside the APC?

Endosomal/lysosomal processing pathway Signup and view all the answers

Which type of cells can present ingested antigens on class I MHC molecules to CD8+ T lymphocytes?

Dendritic cells Signup and view all the answers

What happens if peptides weakly bind to class I major histocompatibility complex (MHC) molecules?

They lead to the degradation of empty MHC molecules Signup and view all the answers

Which type of T cells recognize Class I MHC-peptide complexes?

CD8+ T cells Signup and view all the answers

What is the process called when dendritic cells present ingested antigens on class I MHC molecules to CD8+ T lymphocytes?

Cross-presentation Signup and view all the answers

Where are antigenic peptides generated and bound to class I MHC molecules?

Endoplasmic reticulum Signup and view all the answers

What is the role of CD4+ helper T cells in the immune response?

Recognize Class II MHC-peptide complexes Signup and view all the answers

Which type of antigens can dendritic cells ingest and transport into the cytosol for processing?

Infected host cells Signup and view all the answers

Which type of T cells are presented with endocytosed protein antigens in the MHC pathway?

CD4+ T cells Signup and view all the answers

Where are antigens destined for presentation via the Class II MHC pathway usually internalized from?

Extracellular environment Signup and view all the answers

How are cytosolic proteins tagged for degradation in proteasomes?

Ubiquitin Signup and view all the answers

What happens to antigens destined for presentation via the Class II MHC pathway once they are internalized?

They are degraded in specialized vesicles Signup and view all the answers

What is the term for the initiation of CD8+ T cell responses to antigens in organ transplants and some intracellular microbes?

Cross-presentation Signup and view all the answers

Where do the peptides generated by proteasomes bind to newly synthesized MHC class I molecules?

ER Signup and view all the answers

What is the function of tapasin in the MHC class I pathway?

Association with class I MHC molecules Signup and view all the answers

How are peptide-MHC complexes recognized by CD4+ helper T cells?

On the cell surface Signup and view all the answers

Which molecular pump transports peptides generated by proteasomes into the ER?

TAP Signup and view all the answers

What is the function of tapasin in relation to class I MHC molecules?

Stabilizes peptide binding on MHC molecules Signup and view all the answers

What stabilizes newly synthesized class I MHC molecules in the ER initially?

Chaperones Signup and view all the answers

Which type of T cells recognize peptide-MHC complexes on the cell surface?

CD8+ T cells Signup and view all the answers

What is the main function of proteasomes in the MHC pathway?

Degrade misfolded proteins Signup and view all the answers

Which mechanism allows for preferential loading of high-affinity peptides onto class I MHC molecules?

Tapasin interaction Signup and view all the answers

What is the role of chaperones in the stabilization of class I MHC molecules?

Stabilization in the ER membrane Signup and view all the answers

Where are high-affinity peptides preferentially loaded onto class I MHC molecules?

ER membrane Signup and view all the answers

Where are Class II MHC molecules synthesized?

Endoplasmic Reticulum Signup and view all the answers

What is left in the peptide-binding cleft after the degradation of the invariant chain?

Class II Invariant Chain Peptide (CLIP) Signup and view all the answers

Which protein facilitates the exchange of CLIP with other peptides in the vesicles?

DM Signup and view all the answers

What type of cells do Class II MHC molecules display peptides to?

CD4+ T cells Signup and view all the answers

What type of antigens do Class I MHC molecules bind and display peptides derived from?

Cytosolic antigens Signup and view all the answers

Where are extracellular microbes typically captured?

Phagocytes Signup and view all the answers

What type of T cells recognize peptides displayed by Class I MHC molecules?

CD8+ T cells (CTLs) Signup and view all the answers

Why are T cell-mediated immune responses limited to cell-associated antigens?

Due to intracellular peptide loading and expression of MHC molecules Signup and view all the answers

Which compartments facilitate the processing of ingested proteins into peptides?

Endosomes and lysosomes Signup and view all the answers

What is the function of CD4+ T cells?

Activation of an effector mechanism against extracellular microbes Signup and view all the answers

What is the role of CD8+ T cells?

Elimination of infected or tumor cells Signup and view all the answers

Which type of T lymphocytes are responsible for recognizing protein antigens from cytoplasmic microbes?

CD8+ cytotoxic T lymphocytes Signup and view all the answers

What pathway do protein antigens from extracellular microbes enter for recognition by T lymphocytes?

Class II MHC pathway Signup and view all the answers

What determines the immunodominance of some peptides and the inability of some individuals to respond to certain protein antigens?

Structural constraints on peptide binding to different MHC molecules Signup and view all the answers

What is the role of class I MHC pathway in antigen presentation?

Recognition by CD8+ cytotoxic T lymphocytes Signup and view all the answers

How do T cells recognize nonpeptide antigens?

By altering the peptide-binding cleft of MHC molecules Signup and view all the answers

In some inbred animals, non-expression of certain class II MHC genes led to their inability to respond to:

Simple protein antigens Signup and view all the answers

What do protein antigens from cytoplasmic microbes lead to upon recognition by T lymphocytes?

Killing of infected cells Signup and view all the answers

What is responsible for displaying peptides of protein antigens for immune response generation?

Antigen-presenting cells (APCs) Signup and view all the answers

How are small molecules and metal ions recognized by T cells?

Through noncovalent binding of chemicals to MHC molecules. Signup and view all the answers

What is the role of Class II MHC pathway in antigen presentation?

Recognition by CD4+ helper T lymphocytes. Signup and view all the answers

What are Major Histocompatibility Complex (MHC) molecules responsible for displaying?

Peptides of protein antigens. Signup and view all the answers

Study Notes

The text discusses the importance of linking microbes to specific antigen-processing pathways for effective immune response against intracellular and extracellular microbes.
Protein antigens from cytoplasmic microbes enter the class I MHC pathway and are recognized by CD8+ cytotoxic T lymphocytes, which kill infected cells.
Protein antigens from extracellular microbes enter the class II MHC pathway and are recognized by CD4+ helper T lymphocytes, which activate macrophages to destroy phagocytosed microbes and activate B cells to produce antibodies.
Class I MHC pathway: Antigen presentation to cytotoxic T lymphocytes: cytosolic antigen, antigen presentation, binding to CD8+ T cells, and T cell-dependent effector functions.
Class II MHC pathway: Antigen presentation to helper T cells: macrophage and extracellular microbe in endosome, binding to CD4+ helper T lymphocytes, release of cytokines, macrophage activation, and B cell antibody secretion.
Structural constraints on peptide binding to different MHC molecules determine the immunodominance of some peptides and the inability of some individuals to respond to certain protein antigens.
T cells also recognize and react against small molecules and metal ions in an MHC-restricted manner.
Some inbred animals did not respond to simple protein antigens due to non-expression of certain class II MHC genes, which were later discovered to be involved in antigen presentation.
T cells recognize nonpeptide antigens through covalent modification of self peptides or MHC molecules, or noncovalent binding of chemicals to MHC molecules, altering the peptide-binding cleft and displaying foreign peptide-MHC complexes.
The text answers questions about how rare antigen-specific lymphocytes find antigens and generate appropriate immune responses against extracellular and intracellular microbes by explaining the roles of antigen-presenting cells (APCs) and Major Histocompatibility Complex (MHC) molecules in displaying peptides of protein antigens.

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Description

Test your knowledge about the binding of peptides to class I MHC molecules and their potential to stimulate immune responses. Explore the relationship between peptide binding and the stability of MHC molecules.