Receptors, Recognition Flashcards
(30 cards)
What is the function of the receptors in the innate immunity?
To recognize molecular motifs with invariant and non-rearranging receptros.
Innate immunity is medated by ____ signalling cascades.
Name the different types.
PRR TLR RLR CLR NLR orphan receptors
What can PRRs activate by innate immune sensors?
Interferon Response Factors (IRFs)
NFkB
TLRs 3, 7, 8, and 9 are on the endosomes - what do each of them sense?
TLR3 - dsRNA - viruses
TLR7 - ssRNA - viruses
TLR8 - ssRNA - viruses
TLR9 - CpG DNA (ds) - viruses
Where are NLRs and RLRs located?
What do NLRs induce the release of?
What do RLRs induce the release of?
In the cytoplasm
IL1beta and IL18
Type I IFN and proinflammatory cytokines
What do TLRs induce the release of?
Type I IFN, proinflammatory cytokines (NFkB)
DAMPs are aka _______.
Alarmins
What is the purpose of convergent signalling in the immune system?
In order to ensure that the immune system does not react without cause it requires both a MAMP/PAMP along with a DAMP first to show that damage is being caused by something other than self to which it can react.
How do B cells recognize pathogens?
With BcRs = Ig = Ag binding molecules.
These are macromolecules like proteins, lipids, polysaccharides, and chemicals.
How do T cells recognize pathogens?
With the TcR that binds with the MHC complex that must present processed antigen.
Give a short description of an antibody as secreted by a B cell.
They do not contain transmembrane regions nor do they have cytoplasmic tails.
Where are MHC Class I complexes?
Where are MHC Class II complexes?
What is the difference between the two?
All cells of the body
On all Ag presenting cells
MHC I - has 3 alpha subunits and one beta and presents endogenous peptides but CAN present exogenous through cross presentation to CD8+ T cells.
MHC II - has two alpha and two beta subunits and presents exogenous processed peptides to CD4+ T cells.
How big are each of the MHC complexes?
MHC Class I is able to contain peptides 8-10 AAs INSIDE it and the ends are cleaved if it is too big.
MHC Class II can hold peptides of about 13-17 AAs that can stick outside the complex though will still cleave ends if it is too long.
How do NKT cells recognize pathogens?
They express semi-invariant TcRs that interact with CD1 molecules which present lipids not peptides as antigens.
Define antigen.
An antibody generating protein.
In general they:
- stimulate immune response
- contact intact epitopes recognized by BcR
- Contain processed peptide epitopes recognized by TcRs
Name some APCs.
DENDRITIC CELLS
Also macrophages, monocytes, B cells, epithelial cells, and eosinophils.
List some ways that Ag can be processed.
Autophagy, MIIC/lysosome, proteasome, Exocytic vesicles.
CD1ds are on what kind of cell? What do they recognize?
NKT cells - endo/exogenous lipid Ag
Explain the difference between DC and macrophage response by TLR in early, prolonged, and late responses.
Why are they different?
Why is this important?
Early: Both very similar - TLR recognition and MHC class II to cell exterior.
Prolonged:
DCs stabilize peptide/MHC complexes and migrate to lymph nodes.
Macrophages have transient presentation of peptide/MHC complexes. They effect a CD4+ T cell response and cause infalmmation.
Late:
DCs persist with the MHC complex and prime T cells in lymph nodes.
Macrophages lose MHC complex, decrease CD4+ response, and decrease tissue damage by proxy.
Important because DCs allow priming which takes a while and macrophages stay in the area to effect immediate response. It’s good that macrophages lose T cell effectivity because it would result in tissue damage otherwise.
Describe the difference in DC-T cell contact with and without antigen.
If no Ag = short contact - T cells move on to next immediately
If Ag = long contact - T cells commit Ag to memory.
Describe the TcR CD3 complex.
Both CD4+ and CD8+ T cells have a CD3 complex in juxtaposition to their 4/8+ counterparts. This accounts for the co-stimulation T cells require.
What T cell counterparts react with the following DCs? CD80/86? CD40 DC SIGN OX40L
CD28/CTLA-4
CD40 ligand
ICAM-3
OX40
Describe how a DC creates T cell tolerance.
Describe how a DC creates T cell effectors.
Describe how a DC creates T cell memory.
Resting DC, low Ag, no co-stimulation, short contacts.
Active DC, high Ag, high co-stimulation, cytokines present, long contacts.
Exhausted DC, high Ag, high co-stimulation, short contacts.
The DC determines what of the T cells?
Whether it is on or off.
The type of T cell response.
The population of activated T cells.
