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15 Cards in this Set
- Front
- Back
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where is B cell development antigen independent?
what are the terms given to a developing B cell? |
in the bone marrow.
Pro, Pre, and Immature. |
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B cell development - which stages have what antibodies on their surface?
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Pro has nothing on its surface.
Pre has a Mu (u) heavy chain with a Pre-b light chain. Immature has a complete IgM on its surface. Mature has an IgM and IgD (think mature = MD) Activated = a mature + an antigen, so still has IgM and IgD Memory has IgG and IgA Plasma cell has no surface bound Ig's (just says Ig+) because its secretory. |
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what's the important IL we should know for this development?
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going from Pro to Pre requires IL-7
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Talk about the selection of autoreactive B cells:
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Immature cells in the bone marrow - if they're self reactive, a couple of things happen:
If they react with the multivalent antigen on the stromal cell, the IgM's are crosslinked and this is perceived as a signal to unergo apoptosis. If the immature B cell enrounters a soluble self antigen floating around, its IgM is destroyed and it becomes ANERGIC - it is released, floats around, and expresses IgD and will never react to any antigens. note that Anergic B cells aren't allowed into the primary folicles during circulation - and without the GF's present in the lymph tissues, they'll die out pretty fast. |
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Can B cells be activated without T cell help?
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yes - this is T-cell independent activation. Can come from a polyclonal activator (LPS), or some random kind of random IgM crosslinker.
Note that this will induce the production of IgM only - T cells are needed for isotype switching. |
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what's the big difference between B and T cells in terms of antigen recognition?
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B cells can recognize "native" antigen - so it can perceive random antigens floating around.
T cells need antigens presented to them in the context of MHC. |
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what happens to B cells in the secondary centers after encountering antigen? just generally...
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they expand clonally, are activated, undergo affinitiy maturation and isotype switching, and become memory B cells and effector antibody forming cells.
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how does isotype switching happen?
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T cell mediated - so if you have anything that's not IgM or IgD, it underwent isotype switching. Mediated by IL-4.
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what happens in germinal centers?
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somatic hypermutation and proliferation of B cells. As they replicate, they get more specific. Higher affinity wins out and end up in the apical zone. T helpers outside send in Il4 to initiate isotype switching at the end.
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compare and contrast primary vs. secondary antigen response:
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first time see antigen, get first a lot of IgM, then a whole lot of IgG (requires isotype switching(.
Second time, get IgG as the huge response. So, this requires memory B and memory T cells to get. |
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isotype switching - in what genes do you get this?
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the heavy chains undergo recombination. note that the variable region stays the same here.
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so one more time - what's the job of the germinal center?
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fine tuning of the Ig receptor (somatic hypermutation)
affinity maturation and selection isotype class switching clonal proliferation. CSI - A Clonal proliferation Somatic hypermutation Isotype Switching Affinity maturation/selection. |
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most surface Ig's look like the eventual secreted ones. What's an exception/
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IgM - it's a monomer when on the cell surface, and much bigger when it's secreted by plasma cells.
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weird point - do you glet a greater response if there's lots of antigen or a little antigen?
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little antigen.
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in isotype switching, what gets excised?
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the Mu genes are lost. Left over genes are recombined.
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