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Pathophysiology: Week 4-Lecture 1
Terms in this set (24)
Why does it take so long for a naiive B-cell to start producing antibodies against a specific antigen?
Because multiple inputs are required to activate the cell and most B-cells have to internalize and display the antigen to and activate a Th cell before they become activated
What might be a consequence if somatic hypermutation of B-cells did not occurr?
We wouldn't have any B-cells with higher affinities for antigens, so immune responses would continuously take longer to defend against the same antigens
Which types of antigens are capable of inducing B-cell activation w/o Th cells?
Multivalent polysaccharides (glycan residues) are enough because they are large enough with the same epitopes to bind a bunch of BCRs at the same time
Can multiple B-cells create different antibodies against the same antigen?
No because antigen binding sites (epitopes) are specific to a specific antibody
Would B-cells still activate if they weren't able to act as an APC?
They would only activate when a multivalent polysaccharide antigen bond many of it's BCRs
Why is genetic rearrangement in TCRs necessary for an effective acquired immune response?
TCRs are formed before it ever encounters an antigen, but having a large variety of TCRs means that they are able to sense a larger variety of antigens
Can T-cells differentiate between foreign and host?
Yes. MHCs are specific to host
What is required for the activation of Naiive T-cells? What kind of fine-tuning can the APC do during this process?
Binding of the TCR to MHC (Signal 1) must happen, then the T-cell will be activated when it receives a co-stimulus from a dendritic cell (Signal 2) or cytokines from another immune cell (Signal 3). The types of co-stimulus or cytokines released to the T-cell determine what the T-cell does in the immune response
Why would multiple stimuli be necessary for activation of T-cells?
YES! Needs 2+ stimuli. (MHC and TCR binding with either co-stimulus or cytokines)
What is the difference in response between a naiive cytotoxic T-cell and a memory cytotoxic T-cell that are exposed to the same antigen?
Naiive T-cells need 2 stimuli to activate, but Memory T-cells activate after only 1 stimulus to amount a quick immune response
What kinds of biomolecules are surveyed by T-cells?
MHC (Major Histocompatibility Complexes)
What kinds of T-cells kill virus infected cells? Would this type of T-cell be able to kill the virus infected cells if they didn't express MHC I?
Cytotoxic CD8+ T-cells. No because they only survey MHC I Complexes
What is an MHC composed of and what is it's purpose?
MHCs are antigen displaying complexes found on every nucleated cell
What might be the purpose of having multiple class I an II MHCs?
Different MHCs display different peptides due to differing sequences at binding sites, so the more options you have to display the peptide, the better chance a pathogen antigen will get recognized
How do APCs recognize whether a biomolecule is foreign or host-derived?
Antigens are from proteins that are host-specific
Do APCs display their own protein contents is MHCs? If so, what type of MHCs?
Yes, MHC I
Why is genetic diversity allowed and even a good thing for MHC genes whereas genetic divergence on other genes is risky?
More MHC variants means more antigens that could have an affinity for MHCs to be displayed, but genetic divergence on other genes can encode for proteins that gain/lose functions and cause major problems
Why isn't immunosuppressive therapy required for blood transfusions?
foreign MHC's initiate an immune response, but MHCs are only found on nucleated cells (RBCs dont have nuclei)
What is the purpose of requiring multiple inputs for activation of T and B-cells?
To control their functions so they aren't triggering an immune response constantly, only when it is needed
Can the acquired immune response function dependently of the innate immune system?
No. Co-stimuli from neutrophils and dendritic cells and the complement system are needed
How would the immune response be affected if MHC Class I were not functional APCs? What about MHC II?
APCs would only be able to present through MCH II which would only activate T-cells and immune responses would take longer or miss detecting certain antigen peptides. Same for MHC II, only certain cells could activate and peptides would go undetected
What do booster injections do for B-cells and antibodies?
It stimulates the memory B-cells to keep producing antibodies to fight off the pathogen
What would happen to a virus infected APC?
It would display the viral peptide via MHC I, a Cytotoxic T-cell would bind to the FAS Death Ligand docking site, release granules containing Granzyme B and trigger the apoptosis cascade of the cell
What is "humanized" monoclonal antibody and what is the usefulness of humanizing an antibody?
isolating a B-cell that produces a desired antibody, then fusing it with an immortal myeloma cell which will produce that antibody for life, important for vaccines
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