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77 Cards in this Set
- Front
- Back
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Whydo we need an adaptive immune response?
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Memory
If things get through the innate system, need to plug the holes |
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What are the effectors of the adaptive response?
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Innate response
B-cells + antibodies T-cells |
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What controls the specific response?
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Certain immune responses on the wrong level can kill you
-> if not in control, you can die because your immune system is more powerful than it should be |
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What is diversity and why do we need it?
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We need to fight wtv gets by the innate
Don't want response to be too specific (i.e. just polio) cuz there's a lot we need to fight against Adaptive IR has to be able to adapt to new invaders, be specific but also adaptable and diverse |
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What are antigens?
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Something that elicits an immune response in something else
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What is an epitope?
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Part of an Ag twds which an immune response can be made
There are multiple different epitopes on an antigen There are more than 1 of the same kind of epitope on an Ag, usually need 2+ identical epitopes on an Ag for an Ab to crosslink |
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What is the BCR?
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Receptor on the B cell that an Ag will recognize
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What are Ab? How are they made?
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Ab are ptns that act as flags
Secreted from plasma cells (effector B cells) |
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What happens when there is an infection (i.e. bacterial infection, Humoral)?
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Activate B-cells
B-cell specific for the bacteria binds to it B-cell expresses receptor and waits (if nothing happens at this stage, it dies. 95% of B cell responses require another signal) Need Th cell, whih secretes cytokines and binds to B cell B-cell can get excited and divides, cuz invaders rapidly proliferate (Cell division always occur, may then differentiate into plasma cells) Eventually make Ab that bind to the Ag, which allows innate system to clear the infection |
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What happens if there is a cellular infection (virus)?
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Use T cells (Tc and Th)
Tc doesn't become effective at killing until it gets help from Th |
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What is the TCR?
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Recognizes epitope on An
Does NOT recognize Ag in its active form, only after they go through processing (Only sees Ag in the context of self) |
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Why do we need such specifiity of response by T cells?
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Control
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What is the difference btw the Th and the Tcyt?
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Th: Help B cells make AB, feeds it nfo. Tells other cells what to do
Tcyt: Effector cells, can kill things if they get the right signal |
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How do we distinguish between self and non-self?
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Depends on the epitopes that we see
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What are some APCs?
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Dendritic cells
Macrophages B-cells Certain activated T cells Some activated epithelial cells |
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What is the job of an APC?
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Phagocytose Ag, break it up into little pieces, put it in a MHC, express it
Th sees the Ag in a cloud of self T cell then divides and makes effector cells B cells differentiate: plasma or memory T cells differentiate: Tc or memory Expand amt of defenders vs the pathogen |
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What do Ab do?
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Flags: tell innate response where to go
1)Neutralize 2)Promote opsonization 3)Activate complement 4) Upregulate cell-mediated killing (ADCC) |
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How do Ab neutralize?
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Ab are made to bind to the part of the vius that is required to bind to the cell (neutralizes the ability of the virus to do its job)
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What is opsonization?
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Way in which scavengers of the body can recognize and phagocytose antigens
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What does complement do?
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1)Pro-inflammatory: upregulation of inflammation and recruits inflammatory cells
2)Mrks things: tell recruited cells what needs to be destroyed 3) Punches holes in cells |
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What do Tcyt do?
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Can kill virally infected cells
Can kill cancer cells |
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What would happen if we did not have Tcyt cells?
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We would die
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How does a Tcyt work?
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Caspases are activated
Tcyt shoot things into the cell that causes them to die by apoptosis Important for cell to die by apoptosis because a lot of viruses bud ->If you die by necrosis (punch a hole): way for virus to get release. Neighbouring cells can also get hurt, a lot of collateral damage |
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How many chains is an Ab composed of?
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4 (2 heavy, 2 light)
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What makes up the antigen recognition site?
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Combined variable regions of the heavy and light chains
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What defines what kind of an Ab it is?
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The constant region of the heavy chain
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How is diversity in Ab developed?
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For every Ab, variable domains come from heavy and light chains
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What holds the 2 halves of the Ab together?
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Disulfide bonds
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What kind of strands make up the cst and variable domains of Ab?
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Beta strands (form Beta sheets)
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What are the different types of biding sites in a Fab fragment of an Ab?
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Pocket
Groove Extended surface Protruding surface |
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What kind of structure can an Ab recognize?
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3D structure (can also recognize linear polypeptides)
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What are the noncovalent forces that hold together the Ag:Ab complex?
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Electrostatic forces
Hydrogen bonds Van der Waals forces Hydrophobic forces |
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How is the TCR similar to an Ab?
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TCR ressembles a mb-bound Fab fragment
The variable domains of the heavy and light chains fold to form the antigen binding site |
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What is the difference between an Ab and TCR?
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Transmb domain of the TCR is fixed to he mb
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What is the structure of the TCR?
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α chain linked to a β-chain through a disulfide bond
Both chains have: -variable regions and cst regions -stalk segment -Transmb region -Cytoplasmic tail |
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What is a hypervariable region?
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Region of increased varaibilty
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Where are most of the hypervariable regions in the T cell?
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In the part of the T cel that will see the Ag
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What do T cells see?
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Never see Ag alone
Only see it in context of self (MHC) HLA=MHC |
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What is the structure of an MHC I molecule?
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Heterodimer made up of a mb spanning α-chain and a β2-microglobulin
α chain folds into 3 domains:α1/2/3 α1 & α2 form a cleft/groove α3 stabilizes |
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Which body cells have MHC I?
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All nucleated cells of the body (i.e not RBC)
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What kind of peptides does MHC I bind?
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Peptides that re 8-10 aa long
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How are peptides bound by MHC I?
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By their amino terminal carboxy terminal ends
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How can MHC alleles preferentially bind different groups of peptides?
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MHC are highly polymorphic
(each immune response is different, MHC presents dif peptides btw dif ppl) Have 6 MHC-1, must present right Ag to the right T-cell, in the right orientation |
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Which cells express MHCII?
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Antigen Presenting Cells (APC):
Dendritic cells B-cells Macrophages Activated T- cells |
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What kind of peptides do MHCII bind?
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Peptides that are 13-17 aa in length
Peptide ends are not bound (peptide binding groove is open) |
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How is the peptide held in the groove of MHCII?
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By side chain and interactions between the peptide backbone and conserved aa lining the groove
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Which has more permissive binding of peptides: class I or II?
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Class IIhas more permissive binding
more peptides can fit into the groove (need more diversity at lvl of control) |
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Which region of the MHC-peptide-TCR binding interacts direcly with the Ag?
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Variable regions (especially the hypervariable regions)
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Which cells express MHCII?
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Antigen Presenting Cells (APC):
Dendritic cells B-cells Macrophages Activated T- cells |
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What kind of peptides do MHCII bind?
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Peptides that are 13-17 aa in length
Peptide ends are not bound (peptide binding groove is open) |
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How is the peptide held in the groove of MHCII?
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By side chain and interactions between the peptide backbone and conserved aa lining the groove
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Which has more permissive binding of peptides: class I or II?
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Class IIhas more permissive binding
more peptides can fit into the groove (need more diversity at lvl of control) |
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Which region of the MHC-peptide-TCR binding interacts direcly with the Ag?
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Variable regions (especially the hypervariable regions)
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Which cells express MHCII?
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Antigen Presenting Cells (APC):
Dendritic cells B-cells Macrophages Activated T- cells |
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What kind of peptides do MHCII bind?
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Peptides that are 13-17 aa in length
Peptide ends are not bound (peptide binding groove is open) |
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How is the peptide held in the groove of MHCII?
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By side chain and interactions between the peptide backbone and conserved aa lining the groove
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Which has more permissive binding of peptides: class I or II?
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Class IIhas more permissive binding
more peptides can fit into the groove (need more diversity at lvl of control) |
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Which region of the MHC-peptide-TCR binding interacts direcly with the Ag?
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Variable regions (especially the hypervariable regions)
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Which cells express MHCII?
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Antigen Presenting Cells (APC):
Dendritic cells B-cells Macrophages Activated T- cells |
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What kind of peptides do MHCII bind?
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Peptides that are 13-17 aa in length
Peptide ends are not bound (peptide binding groove is open) |
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How is the peptide held in the groove of MHCII?
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By side chain and interactions between the peptide backbone and conserved aa lining the groove
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Which has more permissive binding of peptides: class I or II?
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Class IIhas more permissive binding
more peptides can fit into the groove (need more diversity at lvl of control) |
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Which region of the MHC-peptide-TCR binding interacts direcly with the Ag?
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Variable regions (especially the hypervariable regions)
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Which cells express MHCII?
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Antigen Presenting Cells (APC):
Dendritic cells B-cells Macrophages Activated T- cells |
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What kind of peptides do MHCII bind?
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Peptides that are 13-17 aa in length
Peptide ends are not bound (peptide binding groove is open) |
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How is the peptide held in the groove of MHCII?
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By side chain and interactions between the peptide backbone and conserved aa lining the groove
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Which has more permissive binding of peptides: class I or II?
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Class IIhas more permissive binding
more peptides can fit into the groove (need more diversity at lvl of control) |
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Which region of the MHC-peptide-TCR binding interacts direcly with the Ag?
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Variable regions (especially the hypervariable regions)
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Why are there 2 types of MHC?
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Control
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What are CD4 cells?
CD8? |
CD4: restricts Th by MHCII
CD8: on surface of Tc, restricted to class I MHC |
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How are T cells defined?
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By what they show on their surface:
CD2/3 CD4/8 |
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What are CD4 and CD8?
What are their structures? |
T-cell co-receptors
CD4: 4 immunoglobulin domains (only 1 chain) CD8: heterodimer of an α and a β chain, that are linked by a disulfide bond |
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What does the CD4 bind to?
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Binds to the β2 dmains of the MHCII molec
This site is different from the Ag combining site seen by the TCR CD4 inc strength of complex binding and Th cell activation |
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What enz does CD4 interaact with in the cytoplasm?
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Lck
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What does the CD8 interact with?
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α3 domain of MHCI
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What happens when CD8 is activated?
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Binds Lck and increases the sensitivity of T cells (affects activition state of T cell)
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What are γδ T cells?
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A minority of T cells that express distinct TCR that are made up of γ and δ chains
Ag recognition is not restricted by MHC I/II but may be b non-classical MHC-like molec These T cells are specialized for specific Ag such as lipids foundin mycobacteria |
