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130 Cards in this Set

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What are some physical barriers to infection?
epithelium, fluid flow, normal flora
What are some phagocytic barriers to infection?
neutrophils and macrophages
During phagocytosis, a lysosome fuses with a ____ to form _____.
phagosome; phagolysosome
Pathogen Associated Molecular Patterns are recognized by ____ on phagocytes.
Pattern Recognition Receptors
What is the MB-lectin pathway?
It's one of the three complement pathways. It reacts to mannose on pathogen surfaces.
How does the secondary response of adaptive immunity differ from the primary response?
It is much quicker and much greater in magnitude.
What is an antigen?
Any molecule that can bind to antibodies or T cell receptors.
Of the four classes of organic molecules, which are the most antigenic?
Proteins by far. Followed by carbohydrates. Nucleic acids and lipids are poor antigens.
What are some properties of a good antigen?
large molecule, structural complexity, neutral
Multiple areas (thousands) on an antigen can bind to different antibodies. These areas are called ____.
epitopes (aka antigenic determinants)
What is the antigen on influenza?
hemagglutin
Vaccines will try to target the bioactive ___ of viruses.
epitopes
What are the four basic kinds of protein in serum? Where will you find antibodies?
albumin, and alpha, beta, and gamma globulins

Gamma globulins are antibodies.
What connects the light and heavy chains and the heavy chains to one another?
interchain disulfide bonds
What gives an antibody its 3D structure?
Intrachain disulfide bonds.
Human antibody shows variability where?
The N terminus end of the heavy chains and light chains.
What are the two families of light chains?
Kappa and lamba (both can exist within each family)
Which Ig families are likely to exist as polymers? What glues together the monomers?
IgA (dimer) and IgM (pentamer)

J chain
Which three classes of antibody exhibit hinge regions?
IgG, IgA and IgD
Are Ag/Ab rxns reversible? What kinds of bonds are made?
Yes. No covalent bonds (ionic, hydrogen, van der Waals, hydrophobic)
What are the antibody classes based on?
The similarities in the C region of the heavy chains.
What kind of Ab might be referred to as tetravalent?
The IgA dimer. It has four binding sites.
Where are the three places you might find Ab?
In serum.
On the surface of B cells in plasma membrane.
Associated with Fc receptors on the surfaces of other cells.
Which antibody is most common in epithelium?
IgE
In connective tissue, which is the most common Ab?
IgG
What is the most common Ab in bodily secretion?
IgA
What's the most common antibody in the fetus? Why?
IgG. It's the only one that can cross the placenta.
What is the predominant class of Ab in serum?
IgG
How do antibodies neutralize viruses?
Typically, they bind to the active epitome on the protein coat. The one that would usually bind to the cell.
How do toxins poison the cell?
They bind to the surface and are taken into cells. Then, the toxic portion gets into the cytoplasm.
How do we vaccinate against toxins?
We make inactive "toxoids" that allow antibody generation.
How do Abs prevent bacterial adhesion?
They binds to and block the adhesive tips of the pili.
What types of cells biosynthesize IgA dimers?
B cells or plasma cells
Where will you find IgA-secreting cells?
Lamina propria.
What is a poly-Ig receptor?
It is on the adluminal aspect of the epithelial cells. By interacting with the J chain of an IgA dimer, it helps transport the dimer across the epithelium and into the lumen.
What part of the poly-Ig remains attached to the IgA in the lumen?
the secretory component
Why do plasma cells of the lamina propria secrete IgA, as opposed to other Ig types?
Something to do with the types of T cells found there.
What is main Ab found in gingival crevicular fluid?
IgG (derived from serum)
What is the main Ab that interacts with cariogenic pathogens?
IgA
What families of Ab have Fc receptors?
IgG, IgA, and Ig E
What is opsonization?
Coating by anything that tags the extracellular pathogen for phagocytosis.
Opsonization is a classic example of the interaction between ___ and ___.
innate; acquired immunity
What are PRR and PAMP?
PRR: pattern recognition receptor
PAMP: pathogen-associated molecular pattern
What are some PAMPs?
dsRNA, mannose, LPS
What is ADCC?
Antibody dependent cell-mediated cytotoxicity. IgG bound to pathogen binds to Fc receptors on NK cells, triggering them to release granules that kill the pathogens.
What two kinds of cells are involved in ADCC?
Eosinophils with FcE receptors and NK cells with FcG receptors.
Does ADCC kill intracellular or extracellular pathogens?
Both.
What kind of receptors are on mast cell surfaces?
FcE
What do eosinophils do? How?
They are associated with killing parasites. They have FcE receptors. IgE coats the parasites and eosinophils release their granules.
What is the importance of IL-5 in the elimination of worms?
Mast cells make IL-5. IL-5 causes production of eosinophils. Eosinophils kill the worms through ADCC
Which complement pathways are innate? Acquired?
Acquired: classical
Innate: MB-lectin and alternative
Which Ab can activate the classical complement pathway?
IgG or IgM pentamers
Where are complement proteins found?
C1 through C9 are all found in serum, but in their inactive forms. (They are activated by proteolysis.)
The classical complement pathway is activated by the binding of either two ___ molecules or an ___ pentamer to the pathogen.
IgG; IgM
The Ab/Ag complex interacts with C1, which then cleaves and activates ___.
C4
C1 has __ globular domains, at least __ of which must be activated to activate the cascade.
6; 2
Only the classical pathway activates __, __, and ___.
C1; C4; C2
The complement proteins __, and ___ can act as opsonins.
C3b; C5a
Some complement proteins enhance vascular permeability, allowing __ and __ to reach the site of infection.
Ab; macrophages
Which complement proteins enhance vascular permeability?
C3a, C4a, and C5a
The terminal complement proteins (C5, C6, C7, C8, and C9) polymerize to form the ____.
membrane attack complex
What are the three things that complement can do?
1. opsonize
2. activate inflammation
3. form membrane attack complex
What are primary lymphoid tissues?
bone marrow and the thymus
_____ cells give rise to B cells, T cells, and NK cells, while ____ cells give rise to all other formed elements of blood.
Lymphoid progenitor; myeloid progenitor
What are CD molecules?
"Clusters of Differentiation"
They are cell surface molecules that are found on immune cells. You can identify the cells by their CDs.
(Re: CDs) All T cells express ___, but will have only one of the following: ___ or ___.
CD3; CD4; CD8
Which CD do B cells express?
CD19
B cell activation is a two step process. What are the steps?
1. Antigen binds to B cell antigen receptor.
2. B cell comes in contact with a T cell, which releases a cytokine that induces differentiation.
When B cells leave the marrow, what kinds of Ab are the showing on their surfaces?
IgM and IgD
What is class switching?
When the B cell stops secreted IgM and switches to IgE, IgA, or IgG or becomes a B memory cell.
How does the memory B cell differ from the original B cell?
It's threshold for activation is lower.
In the absence of T cell cytokines, the activated B cell will differentiate into what?
An IgM secreting plasma cell.
What is a T dependent antigen?
Requires the communication of T and B cells to be neutralized.
What kinds of molecules are T dependent? T independent?
T dependent: proteins
T independent: carbs, FAs, and NAs
What kind of antibodies are produced during T independent activation?
IgM
Is graft rejection a response from the innate or acquired system?
acquired
Is graft rejection mediated by T cells or B cells?
T cells
Describe the structure of MHC I and MHC II.
They are both heterodimeric glycoproteins. They are noncovalently associated.
Both have a groove that acts as a peptide binding site.
MHC I is expressed on all ____ cells in the body.
nucleated
Which cells express MHC II?
B cells, macrophages, dendritic cells, and some activated T cells.
Which subunit of MHC I does not integrate into the cell membrane?

What are the other three parts?
beta2-microglobulin

a1, a2 and a3 (a3 inserts into membrane)
What are the four subunits of MHC II? Which ones insert into the cell membrane?
a1, a2, b1, b2

a2 and b2 insert into the cell membrane
Which kind of MHC has b2-microglobulin? What's unique about its genetic origin?
MHC I. b2-microglobulin is encoded for on a different protein
Human MHC is highly ____, meaning many phenotypes are possible.
polymorphic
How is MHC inherited?
It is codominantly expressed. You get one set of genes from mom, one from dad. All combos are possible. Each cell has both kinds.
What are the B cell surface antigen receptors?
antibodies
What is positive and negative selection in the thymus?
Negative: cells that interact strongly with self-antigen are eliminated.

Positive: Cells that are capable of interacting with MHC.
About what percentage of double positive cells are eliminated? Why?
About 95% of double positive cells die because they are potentially auto-reactive.
Like B cells, T cells are ____, meaning they only express one kind of antigen receptor.
monospecific
What is a naive B or T cell?
A B or T cell that has not yet encountered its antigen.
CD8 T cells generally become ___. CD4 T cells generally become ___.
cytotoxic T cells; helper T cells
What are the two T helper subsets we will look at?
TH1 and TH2
For a CTL to kill a cell, what two things must be present on the cell surface?
The foreign antigen and the self MHC.
CD4 T cells only recognize foreign antigens on an antigen-presenting cell under what circumstances?
The antigen must be bound to MHC II.
CD8 T cells only recognize foreign antigen when it is bound to what?
MHC I
What kinds of antigens do T cells react against?
proteins
How does the professional antigen presenting cell get the antigen and present the antigen?
It digests the antigen intracellularly, associates them with MHC and re-expresses them on the cell surface.
What are "professional" antigen presenting cells?
Those with MHC II, e.g. macrophages, dendritic cells, B cells, some T cells
How do professional antigen presenters get the antigen in the cell?
endocytosis
How does the antigen get into non-professional antigen presenters?
They are within the cell, like viruses.
Peptides are required for MHC presentation. So, how do perfectly healthy cells get MHC on their surfaces?
They put self peptides in the MHC, so, theoretically, the T cells should not recognize it.
The structure of the T cell antigen receptor is kind of like the MHC II structure. How?
Both have an alpha and beta chain, each of which has a transmembrane region.
What is alloimmunity?
When an individual gains immunity to a part of another member of the same species, as with an organ transplant.
T cell activation involves what two steps?
1. The T-cell receptor interacts with the peptide/MHC combo.
2. Secondary signals from the antigen-presenting cells.
What is alloimmunity?
When an individual gains immunity to a part of another member of the same species, as with an organ transplant.
T cell activation involves what two steps?
1. The T-cell receptor interacts with the peptide/MHC combo.
2. Secondary signals from the antigen-presenting cells.
Which receptors recognize conformation dependent epitopes?
Only antibodies can. The T cell receptors only recognize short (perhaps linear) peptides.
Is B and T cell specificity determined before or after they encounter antigen?
before
When T cells are activated, they start showing a receptor for which cytokine? Which cell produces this cytokine?
IL2
T helpers themselves often secrete IL2, so T helper activation is often (but not always) required for T cytolytic activation.
Do activated CD8 T cells require secondary signals to work?
No. They're active. They just need to recognize the peptide on MHC I
What are the two major kinds of CTL effector molecules we discussed?
perforins and granzymes. The perforins let the granzymes in. The granzymes activate caspases and the cell undergoes apoptosis.
How does the acquired system cause osmotic lysis?
If IgM or IgG binds to an antigen, it can activate the classical complement pathway, which will form the membrane attack complex.
How do CTLs help prevent tumors?
Tumor cells display abnormal peptides (pieces of oncogenes) on their MHC I.
How are subsets of T cells differentiated?
By the kind of cytokines they secrete.
What do TH1 cells do?
Activate macrophages (this is the most important thing); induce B cells to produce opsonizing antibody (typically IgG).
What do TH2 cells do?
Predominantly, they activate B cells.
They also have some effects on macrophages.
What is the classic TH1 cytokine?
gamma interferon (IFN-gamma)
What are the two TH2 cytokines I want to remember?
IL-4, IL-5 (involved in parasite infection)
Which kinds of T cells activate macrophage?
TH1

(TH2 may actually suppress macrophages)
What kind of T cell induces formation of IgE?
TH2
What does gamma interferon do?
In activates macrophages and produces IgG that enhances opsonization.
Why are TH1 cells said to be involved in cell-mediated immunity?
They activate CELLS (macrophages and neutrophils) to induce killin
Tuberculosis bacteria like to live within ____. They prevent fusion with ___. However, TH1 cells may be able to overcome this effect.
phagosomes; lysosomes
If you have a positive TB test, you get an xray to check for ____, which are basically large clusters of ____ surrounded by ___.
granulomas; macrophages; TH1 cells
Quick immune reactions are mediated by ___ binding to ___ cells. Delayed hypersensitivity is mediated by cytokines released by___.
IgE; mast cells; TH1
How does the TB test work?
It's a delayed allergic response. The memory cell response causes a reaction.
Things to know about TH2
IL-4: activates mast cells (with IgE)
IL-5: activates eosinophils
IL-10: suppresses macrophages
Define:
Syngeneic
Allogeneic
Xenogeneic
Syngeneic: genetically identical graft
Allogeneic: graft from same species
Xenogeneic: graft from different species
What is hyperacute rejection?
Very quick reaction against foreign (human) MHC. Indicates previous exposure to foreign MHC.
Which kinds of antibody DO NOT have Fc receptors?
IgM and IgD