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42 Cards in this Set

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What is required for B cells become activated? How do B cells do this?
Cross linking of their receptors. They cluster their receptors on the surface. Internally, receptors are linked by Syk, a molecule that further signals when both receptors are bound.
What is a common coreceptor in B cell activation? Explain how it works.
Complement receptor. The B cell contains CR1, which, when it binds C3b on a pathogen, causes C3b to under cleavage to C3D. C3D then binds CR2 (with Cd19 and 81)on the B cell and reinforces the cross link signal.
What are the two types of Ag that B cells produce Ab against?
T independent Ag and T dependent Ag.
What are the Two types of T independent Ag? Do T independent Ag have memory? What Ab do these Ag produce?
TI-1 and TI-2.
TI-1 stimulate Toll cell receptors
TI-2 are repetitive epitopes that activate B-1 B cells.
No memory, primarily IgM response.
Do T-dependent Ag invoke a memory immune response?
Yes! Results in Somatic Hypermutation and isotype switching.
Which kind of Ag, TI or TD, results in somatic hypermutation and isotype switching?
T dependent.
Can Athymic individuals mount an immune response to TI ag? TD?
yes to TI, no to TD
Give two examples of TI-1 ag.
Bacterial LPS and Bacterial DNA
What kind of Ag is produced in the fetus, doesn't require T help, and recognizes polysaccharides and (a repetitive epitope)?
TI-2
Compare TI-1 ag activation of B cells and TI-2 ag activation of B cells.
TI-1 ag bind BCR, costimulatory, and some other activating receptor on the b cell. TI-2 ag activates the Bcell via extensive receptor crosslinking.
What is required for B cells become activated? How do B cells do this?
Cross linking of their receptors. They cluster their receptors on the surface. Internally, receptors are linked by Syk, a molecule that further signals when both receptors are bound.
What is a common coreceptor in B cell activation? Explain how it works.
Complement receptor. The B cell contains CR1, which, when it binds C3b on a pathogen, causes C3b to under cleavage to C3D. C3D then binds CR2 (with Cd19 and 81)on the B cell and reinforces the cross link signal.
What are the two types of Ag that B cells produce Ab against?
T independent Ag and T dependent Ag.
What are the Two types of T independent Ag? Do T independent Ag have memory? What Ab do these Ag produce?
TI-1 and TI-2.
TI-1 stimulate Toll cell receptors
TI-2 are repetitive epitopes that activate B-1 B cells.
No memory, primarily IgM response.
Do T-dependent Ag invoke a memory immune response?
Yes! Results in Somatic Hypermutation and isotype switching.
Which kind of Ag, TI or TD, results in somatic hypermutation and isotype switching?
T dependent.
Can Athymic individuals mount an immune response to TI ag? TD?
yes to TI, no to TD
Give two examples of TI-1 ag.
Bacterial LPS and Bacterial DNA
What kind of Ag is produced in the fetus, doesn't require T help, and recognizes polysaccharides and (a repetitive epitope)?
TI-2
Compare TI-1 ag activation of B cells and TI-2 ag activation of B cells.
TI-1 ag bind BCR, costimulatory, and some other activating receptor on the b cell. TI-2 ag activates the Bcell via extensive receptor crosslinking.
Where does T cell dependent activation of B cells occur (specific location in tissue)?
In the T cell zone of the lymph node.
Explain what happens in T cell dependent b cell activation.
A naive CD4 Th cell is presented with Ag by a dendricite. Meanwhile, a naive B cell binds Ag and becomes trapped in the T cell zone of the lymph node. The Ag activated B cell CD40 receptor binds CD40L on the Th cell, creating a second signal. This produces cytokines that further activate the B Cell
What is CD40?
What cell is it on, what does it bind and what cell it that molecule on?
CD40 is receptor on B cells that binds CD40L on Th cells. This results in the release of cytokines that further activate the B cell.
What do follicular dendritic cells do?
They present Ag to T cells/B cells like regular dendritic cells, however, they can bind and preserve Ag for extended periods of time.
In what part of the lymph node are Ag activated B cells found?
What occurs here?
The germinal centers. Somatic hypermutation, isotype switching, and affinity maturation.
Explain the fate of a B cell in a germinal center of a lymph node (centrocyte) after somatic hypermutation.
If the centrocyte doesn't bind Ag with high affinity after SH, it undergoes apoptosis. If it does bind Ag with high affinity, the B cell receptor is cross linked with Ag and binds T helper cell (via CD40, CD40L), receives cytokines and proliferates. It can now undergo Isotype switching (requires CD40/CD40L).
What syndrome results from a lack in CD40L on T helper cells?What problem does this cause?
Hyper IgM syndrome. Without CD40L, isotype switching cannot occur and all you have is IgM!
Compare a resting B cell to a plasma B cell using the following Attributes:
Contain Surface Ig?
Surface MHC II?
High Ig secretion rate?
Inducible growth?
Inducible Somatic HM?
Inducible Isotype switching?
Resting B Cell- has Surface Ig, plasma doesn't
Resting B Cell has surface MHC II, plasma doesn't
Resting B cell does not secret lots of Ig, Plasma Does
Resting B cell has inducible growth, SHM, and Isotype Switching, But the plasma cell isn't capable of any of those things.
Which B cells fight today's infection and which B cells fight tomorrows infection?
Plasma Cells fight today's infection, memory B Cells fight tomorrow's.
What molecules drive the differentiation of a Centrocyte into either a plasma cell or a Memory B cell?
If centrocyte receives IL-10, it will become a plasma cell. If it receives IL-4, it becomes a memory B cell.
Which Igs protect blood and extracellular fluids?
IgA, IgM, and IgG
Which Igs can be transported across epithelial surfaces by specific receptor proteins?
IgA and IgG
Explain how IgG is transferred across an epithelial surface.
This IgG is endocytosed with FcRn. In the vessicle, the acidic pH causes FcRn to associate with IgG, protecting from degradation. When the vessicle reaches the other side, the basic pH Causes FcRn to dissociate.
Explain how IgA is trasferred across an epithelial surface.
IgA binds poly Ig receptor, is endocytosed, then brought to the other side.
What Ig is passively given to the fetus during gestation?
IgG
What Ig is given to an infant while breastfeeding?
IgA
What Igs are really good at fixing complement?
IgM, Ig1 and Ig3
Why is IgM so good at fixing complement?
Its' pentameric form binds lots of molecules with low affinity (b/c no Somatic Hypermutation). When bound to 10 ag, they are oriented in a way that facilitates complement binding!
What two molecules initiate the classical complement pathway (binding to molecule C1)?
IgM and C-reactive proteins can bind to c1
How are immune complexes cleared from the body?
Erythrocytes bind complement/ag complex and bring them to the spleen and liver for disposal.
Which subclass of IgG has a hinge that is most susceptible to proteolytic cleavage? Why is this useful in vivo?
IgG class III - b/c it has that extended neck. This allows the IgG to bind complement better
What immune cell is invovled with ADCC? What receptors do these cells recognize?
Natural killer Cells...they bind pathogens that are coated with Ig and have crosslinked Fc receptors.