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16 Cards in this Set
- Front
- Back
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What is humoral immunity? What cell is most responsible for it?
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Humoral immunity is the immune response based on antibodies. B lymphocytes are primarily responsible
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What Ig is associated with teh primary humoral response? Secondary?
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Primary --> IgM
Secondary --> IgG |
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True or false: the secondary humoral response applies to both thymic dependent and thymic independent antigens
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False; only thymic dependent
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What is isotype switching? What switch usually occurs?
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A particular Ab changes from one type of Ig to another; the specificity does not change, only the overall structure/type.
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True or false: IgG experiences affinity maturation
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True; IgM does not
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What is the relationship between antigen dose and degree of affinity maturation?
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Large antigen dose, less affinity maturation. Inverse relationship.
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What two signals are required in B cell activation?
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1) The Ag itself binding a B cell receptor
2) The T cell receptor (TCR) binding the MHC-presented antigen on the B cell |
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What triggers isotype switching in the B cell?
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The release of cytokines by helper T cells in the activation process; thus
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When activated, what cells do B cells differentiate into?
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1) Plasma cells
2) Memory B cells |
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Where do we see Igalpha and Igbeta?
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They are associated with the intermembrane Igs that are involved in B cell activation. They couple binding of the Ig to an intracellular response; signal transduction molecules. The Ig has a small intracellular tail and cannot trigger a big process.
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In the B cell, what is triggered by antigen cross-linking of two B-cell receptors?
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This is the first signal in B cell activation.
When the antigen cross-links the receptors, src tyrosine kinases (Blk, Fyn, Lyn) phosphorylate the ITAM domain of the Igalpha and Igbeta molecules (Pi added to tyrosine). Syk kinase then binds the phosphotyrosine. Triggers cascade of events that result in proliferation, differentiation. |
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What does ITAM stand for? Where do we see ITAM domains?
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ITAM = Immunoreceptor tyrosine-based activation motif
Seen in Igalpha and Igbeta of B cell receptor |
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What does activated Syk tyrosine kinase bind?
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Igbeta
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How does bcl-2 relate to B cell activation?
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B cells with high Ag affinity are selected for. If a B cell shows high affinity, bcl-2 is ligated, and the B cell can express the "survival gene"; otherwise apoptosis
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Where are germinal centers seen? What important thing occurs here?
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Within lymph nodes. Positive selection for B cells with high affinity receptors; binding of Th cells and B cells.
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True or false: bcl-2 activation encourages apoptosis
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False; the ligation of bcl-2 prevents apoptosis
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