Ag Processing Flashcards
What is antigen processing?
Antigen processing is the breakdown of proteins into peptide fragments that are presented by MHC molecules to T cells.
How do MHC class I and MHC class II differ in antigen presentation?
- MHC class I presents endogenous (intracellular) antigens to CD8+ cytotoxic T cells.
- MHC class II presents exogenous (extracellular) antigens to CD4+ helper T cells.
What are the two main pathways of antigen processing?
The endogenous (cytosolic) pathway for MHC class I and the exogenous (endosomal) pathway for MHC class II.
Which cells are professional antigen-presenting cells (APCs)?
Dendritic cells, macrophages, and B cells.
What is the role of the invariant chain in MHC class II processing?
It prevents premature peptide binding and is later replaced by antigenic peptides in endosomes.
T cells require antigen presentation via MHC molecules to
recognize antigens.
Proteasomes degrade cytosolic proteins into peptides for
MHC class I presentation.
The transporter associated with antigen processing (TAP) transports peptides into the ER for
MHC class I loading.
HLA-DM facilitates peptide exchange on
MHC class II molecules.
Cross-presentation allows extracellular antigens to be presented via
MHC class I.
MHC class II molecules present intracellular peptides.
False
Dendritic cells are the most effective professional APCs.
True
Proteasomes are involved in the exogenous antigen processing pathway.
False
CD4+ T cells recognize antigens presented by MHC class I.
False
Peptides presented by MHC class I originate from ______________ proteins.
Intracellular
The transporter responsible for moving peptides into the ER for MHC class I loading is ______________.
TAP
MHC class II presents peptides to ______________ T cells.
CD4+
The major histocompatibility complex (MHC) is also known as ______________ in humans.
Human Leukocyte Antigen, HLA
Which molecule stabilizes immature MHC class II molecules before peptide loading?
a) TAP
b) Invariant chain
c) HLA-DM
d) Calreticulin
Answer: (b) Invariant chain
Which antigen-processing pathway is primarily used for viral peptides?
a) Endosomal pathway
b) Exogenous pathway
c) Cytosolic pathway
d) Lysosomal pathway
Answer: (c) Cytosolic pathway
Which APC is most effective in activating naïve T cells?
a) Macrophages
b) B cells
c) Dendritic cells
d) Neutrophils
Answer: (c) Dendritic cells
A patient with a viral infection has increased CD8+ T cell activity. Which antigen-processing pathway is being used?
The endogenous (cytosolic) pathway, where viral peptides are presented by MHC class I to CD8+ T cells.
A person receives a tissue transplant and experiences immune rejection. What molecules are primarily responsible?
MHC molecules, as they present non-self antigens that activate T cells against the transplanted tissue.
A bacterial toxin is phagocytosed and presented to CD4+ T cells. Which MHC pathway is involved?
The exogenous (endosomal) pathway, where peptides are presented via MHC class II.
Antigen Processing:
The breakdown of antigens into peptides for MHC presentation.
Antigen Presentation:
The display of processed peptides on MHC molecules for T cell recognition.
Proteasome:
A protein complex that degrades intracellular proteins for MHC class I presentation.
Invariant Chain:
A protein that stabilizes MHC class II before peptide loading.
Cross-Presentation:
The process by which exogenous antigens are presented on MHC class I molecules.
