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36 Cards in this Set
- Front
- Back
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Which muscles does MG primarily affect?
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Cranial and limb muscles
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Does weakness vary with MG?
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Yes
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Is MG due to a lack of innervation?
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Not at all
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What reverses the effects of MG?
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Anti-cholinesterases
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What area of the body is usually the first area affected by MG?
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The eyelids
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When looking at a compound action potential in a MG pateint, is there a steady increase or decrease of the action potential?
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Decrease
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When does a muscle fatigue in a patient with MG?
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When it is repeatedly stimulated.
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What substance was used to purify AchRs?
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Alpha-bungarotoxin
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When using radio labeled aplha-bungarotoxin, what discovery about the AchR receptors on a MG patient was found?
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They didnt have as many as an unaffected person.
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What happened when scientists injected AchRs into rabbits?
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They developed antibodies against the AchRs and developed a MG-like disease.
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How many subunits are there in a AchR?
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5 subunits
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Which subunit has the site where the anti-AchR antibody binds? What is that regoin called? Which residues?
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The alpha subunit; the main immunogenic regoin - 61-76
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Do the antibodies against AchRs bind where acetylcholine binds?
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No they bind at the main immunogenic region.
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What percentage of antibodies bind at the main immunogenic region?
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75-80%
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Can you induce MG by just injecting the Ab?
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Yes
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What is the only requirement of the AchR antibody?
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That they bind to the MIR.
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How does the binding of the antibody cause MG?
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Crosslinking causes an increased rate of internalization of the recptor at any given time. Basically you have less receptor.
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What is the internalization rate of crosslinked AchRs?
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2-2.5 days
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How does MG affect the surface of the post synaptic terminal? What does this cause?
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Instead of being convolulted, it is flatter. There is not as much surface area for binding and it isn't as easy to trap Ach.
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What EPP do you need to evoke an action potential?
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-45 mV
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Is an MG patient's EEP increased or decreased? What affect does this have on the patient?
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It is decreased and thus it is easier for the patient to drop below threshold with a small decrease in Ach due to repetitive stimulation.
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What are the proliferation of AchR antibodies dependent on?
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T-cells - T cells have to activate B-cells in order for them to start producing the antibodies.
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What do T-cells secrete to help the B-cells to differentiate?
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Cytokines
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Do T cells and B cells recognize the same epitope on the AchR?
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No they recognize different epitopes.
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What type of cell presents the AchR to the T-cells?
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Antigen presenting cells (MCH molecules)
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What must an antibody have to interact with its antigen?
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Complimentary surface contours
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What do you call an antibody to a specific antigen?
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Idiotype
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What do you call and antibody to an idiotype?
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anti-idotype
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What is an algorhythm for designing complementary surface contours?
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Complementary hydropathic patterns
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What is a peptide that is complimentary for the MIR called?
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Antigen receptor mimetic (ARM)
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What happens if you immunize with an ARM?
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It produces antibodies that are complimentary to the ARM. That means that antibodies are made that can bind to the ARM and since the ARM is has the same surface contour as the the anti-AchR, they bind to it.
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How does a T Cell vaccine work?
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Anitbodies that are specific for the T cell receptor that binds to AchR are produced. This prevents the T Cell from binding to the AchR and releasing cytokines that would induce B-cells to start making antibodies.
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How does a B cell vaccine work?
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Antibodies bind to the immunoglobin on the surface of the B-cell preventing it from making the anti-AchR antibodies.
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What is different about the make-up of a dog's esophagus that makes them more likely to choke or have megaesophagus?
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Their esophagus is composed of a higher ratio of skeletal muscle which is what is fatigued in MG.
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How do most dogs with MG die?
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Aspiration pneumonia due to their esophageal problems.
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What was the best combination of T-Cell and B-Cell vaccination order in the MG dogs?
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Giving the T-Cell and B-Cell vaccines at the same time.
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