Exam 2: Dr. Pinchuk Antigen Processing and Presentation Flashcards
In what form does TCR antigen recognition occur?
Only in the form of peptide bound to an MHC molecule on the surface of APC
What are the 2 things that occur in TCR antigen recognition?
Antigen processing and antigen presentation
What is antigen processing?
Pathogen-derived proteins must be degrade into peptides by APCs
What is antigen presentation?
When peptides are assembled into peptide:MHC complexes for display on the APC surfaces
What are the steps to antigen processing and presentation?
Protein antigen is in the cell
Antigen processing occurs by breakdown of protein
Presentation of peptide by MHC molecule
What do the 2 classes of MHC present antigens to?
CD8 and CD4 T cells
What co-receptor is MHC class I associated with?
CD8
What co-receptor is MHC class II associated with?
CD4
What do MHC molecules bind?
A variety of peptides in different intracellular compartments
What does TCR specifically recognize?
Both peptide (foreign) and MHC (self) molecules
What are dendritic cells?
Universal antigen presenting cells
The best presenting cells
What are macrophages when they are in blood circulation?
Monocytes
Where are dendritic cells located in the lymph node?
T cell areas
How do dendritic cells do antigen uptake?
Macropinocytosis and phagocytosis by tissue dendritic cells
Viral infection
What is MHC expression like in dendritic cells?
Low on tissue DCs
High on DCs in lymphoid tissues
What is the co-stimulatory delivery of DCs?
Constitutive by mature, nonphagocytic lymphoid dendritic cells
What is the antigen presented to DCs?
Peptides
Viral antigens
Allergens
What is the location of DCs?
Ubiquitous throughout the body
What is the process of antigen uptake in macrophages?
Phagocytosis
What is MHC expression like for macrophages?
Inducible by bacteria and cytokines
What is the co-stimulatory delivery for macrophages like?
Inducible
What is the antigen presented to macrophages?
Articulate antigens
Intracellular and extracellular pathogens
What is the location of macrophages?
Lymphoid tissue
Connective tissue
Body cavities
What is the location of B cells in the lymph node?
Follicle
What is antigen uptake like for B cells?
Antigen-specific receptor
What is MHC expression like for B cells?
Constitutive
Increases on activation
What is the co-stimulatory delivery like for B cells?
Inducible
What antigen is presented to B cells?
Soluble antigens
Toxins
Viruses
What is the location of B cells?
Lymphoid tissue
Peripheral blood
What makes B cell different than other APCs?
It belongs to the adaptive immune system
What cells do not have MHC class I?
RBCs
What do immature DCs do?
Uptake and process antigen
What do mature DCs do?
Present antigen
Where are immature DCs located?
Peripheral tissues
Where are DCs that are processing antigen located?
Lymphatic location
Where are mature DCs located?
Lymphoid tissues
What are the 2 models of DC maturation?
Classical model
Revised model
What happens in the classical model?
Pathogen-induced migration
What happens in the revised model?
Steady state migration
Pathogen induced migration
What is pathogen-induced migration?
Migration of immature DC from the periphery to the T cell areas of the lymph nodes only in response to microbial stimulation (infection)
What is steady state migration?
Occurs constitutively in the apparent absence of microbial stimulation
The mechanism by which DCs can sample and engulf self-proteins and “food antigens” to naive T cells to establish and maintain peripheral tolerance to such antigens
What is the rule of antigen presentation for direct presentation with MHC class I?
Peptides generated in the cytosol are transported into the endoplasmic reticulum, where they bind MHC class I and presented to CD8 T cells
What is the rule of antigen presentation for direct presentation with MHC class II?
Peptides generated in acidified intracellular vesicles presented by MHC class II and presented to CD4 T cells
What is the exception to antigen presentation for cross-presentation?
Allows extracellular antigens to be processed and displayed within MHC class I to CD8 T cells
Why can cross-presentation be done?
Because it enhances MHC
What is the second exception to antigen presentation?
Peptides from pathogens that can flourish in the cytosol can cross over
What are peptides processed through?
Proteosomes
What kind of antigen presentation is receptor-mediated endocytosis of bacteria?
Direct presentation
What kind of antigen presentation is macropinocytosis of bacteria or viruses?
Direct presentation
What kind of antigen presentation is viral infection?
Cross-presentation
What kind of antigen presentation do exogenous viral antigens use?
Cross-presentation
What kind of antigen presentation is transfer of viral antigens from infected DC to resident DC?
Cross-presentation
Look at direct and cross-presentation picture
Look at direct and cross-presentation picture
What can cross presentation explain the direct presentation cannot?
How CD8 T cells responses are primed to infectious organisms that do not infect APCs
How DCs prime cytotoxic T cells against pathogens that are restricted to the endocytic pathway and never reach the cytosol
Pathogen infected DCs are often functionally compromised, but they present antigens efficiently
What is dendritic cell nibbling?
Cross-presentation
DC meets the infected cell and chops the head off of the infected cell (extracellular uptake)
What is autophagy?
Presentation of cellular antigens by MHC class II Self-eating
In the research that discovered autophagy, why were yeast systems used?
They multiply quickly and generate multiple clones
What are the principal manifestations of immunological autophagy?
Direct pathogen elimination
Regulation and effector functions of PRRs
Regulation of inflammasome activation and alarming secretion
Cytoplasmic antigen processing for MHC II presentation and T cell homeostasis
What cells express MHC class I?
T cells B cells Macrophages DCs Neutrophils
What cells express MHC class II?
B cells
Macrophages
DCs
Thymic epithelium
What is degenerate binding specificity?
MHC molecules have peptide-binding sites that are capable of binding peptides of many different amino acid sequences
What is the peptide-binding groove?
The peptide-binding site on the surface of the MHC molecule with which a single peptide is held tightly by non-covalent bonds
