Diebel- Antigen presentation and processing Flashcards
Describe the life of a cell in the immune system….
Differentiation:
Immature > mature >
Activation/Induction:
Resting > Activated (Effector) > Memory > activated
What is anergy?
Anergy is a way to weed out cells and prevent auto-immunity. It occurs when a T cell binds self antigen w/ out co-stimulatory molecule present (B7)
What do you need for full T cell activation?
Dual signaling!
The act of the APC ingesting antigen and breaking it down stimulates the expression of B7. Dual signaling required proper Tcr and co-stimulatory interarctions.
What is CTLA-4?
Regulates T cell response over a fixed period of time
T cell presented CD28 eventually turns into CTLA4 which still binds to APC but inhibits it. This ensures that the cell only performs it’s functions for 3-4 days.
Most cells in the body present both ___________using _________which is recognized by _______.
Foreign and self antigens
MHC I
CD 8 killer T
Professional APCs also present antigens using ______ which is recognized by___________.
MHCII
CD 4 helper T
Which is the most effective APC?
Dendritic cells
B7 is equivalent to what CD?
CD80/86
Immature Dendritic Cells
MHCII expression?
B7 C0-stimulation expression?
both are constitutively expressed at low levels
Mature dendritic cells
MHCII expression?
B7 C0-stimulation expression?
Both are constitutively expressed at high levels
Macrophages
MHCII expression?
B7 C0-stimulation expression?
MHCII- must be activated by phagocytosis to express
B7- must be activated to express
B cells
MHCII- constitutively expressed (increases w/ activation)
B7- must be activated to express
Compare the cytosolic and endocytic pathway.
Cytosolic:
intracellular protein synthesis of endogenous antigen–>RER–>MHCI–> surface
Endocytic:
MCHII made in RER–> cell takes up exogenous antigen from environment–> put on MHCII–> surface
Proteins in the cell are degraded by ______. What are it’s components?
Proteasomes!
20S component- active part involved in breaking down the protein into bits
19S lid-recognizes and binds ubiquitin
What is ubiquitin?
Tags things like viruses to be bound to 19s regulator and thrown away in the proteasome trash can.
What triggers a proteasome to switch out it’s components and become an immunoproteasome? Why is this impt?
TNFa
IP is more efficient at degrading protein to the right size/charge to load onto MHC complexes.
What happens when IP is present (i know this is redundant…)?
You break down proteins and load them onto MHCI MUCH BETTER than a constitutively active proteasome.
What is TAP?
transporter associated with antigen processing
What does TAP do?
TAP proteins extend across the RER membrane and transport cytosolic peptides into the lumen of the RER where peptides are being loaded onto Class I molecules.