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KN-Immunology Block 1 > L8: B cell-mediated immunity I > Flashcards

L8: B cell-mediated immunity I Flashcards

1
Q

What is the main function of B cells?

A

produce antibodies

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2
Q

What is somatic hypermutation?

A

allows B cell responses to increase in affinity as they develop

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3
Q

What is isotype switching and what benefit does it provide?

A

Allows B cell responses to be tailored to best deal with the particular pathogen

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4
Q

How can B cell responses be retained?

A

In the form of memory B cells, providing lon-lived immunity to re-infection

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5
Q

What is the first signal of activation for a B cell? The second?

A

First is recognition of its cognate determinant in an antigen by BCR.
Second is activation by TH1 or TH2 cell.

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6
Q

Where do B cells proliferate and differentiate?

A

In germinal centers

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7
Q

What is the signal transduction unit for the BCR?

A

the Ig-alpha and Ig-beta complex.

This requires cross-linking of multiple antigen-receptor complexes

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8
Q

What is complement receptor 2 (CR2)?

A

It is the B cell co-receptor. It binds to a breakdown product of C3b (C3d)

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9
Q

If a B cell is activated, but there are no activated effector T cells, what is the antigen likely? What else could it be?

A

the antigen is likely a self-molecule and this is a method of tolerance.
It could also be a non-protein determinant of a pathogen.

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10
Q

What is a T-independent antigen?

A

a non-protein antigen that can elicit B cell activation in the absence of T cell help

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11
Q

What are TI-1 antigens? How do they work?

A

TI-1 antigens have an intrinsic capacity for inducing B cell proliferation. They engage the BCR as well as the pattern-recognition receptors on B cells. AKA mitogens

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12
Q

What are TI-2 antigens? How do they work?

A

TI-2 antigens act by heavily crosslinking BCRs on the surface of the B cell.they are usually composed of cell wall polysaccharides.

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13
Q

What will high concentrations of mitogen do?

A

polyclonaly activate B cells. This only happens in lab experiments

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14
Q

What can low concentrations of TI-1 mitogens do?

A

elicit an antigen-specific IgM response

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15
Q

Can infants have a TI-2 antigen response?

A

no. It takes 1-5 months for B1 B cell populations to build up

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16
Q

Where are germinal centers established?

A

within lympoid follicles

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17
Q

What is happening in germinal centers?

A

somatic hypermutation results in B cells with higher or lower affinity for antigen.
Cytokines produced by helper T cells promote isotype switching
Positively selected high-affinity isotype-switched B cells differentiate into memory and plasma cells.

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18
Q

What does IL-5 promote class switching to?

A

Augments production to produce IgA

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19
Q

What does IL-4 do?

A

Induces change to IgE

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20
Q

Can plasma cells be induced to proliferate?

A

No, they are permanently differentiated.

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21
Q

Do plasma cells have Surface MHC class II?

A

No

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22
Q

Do plasma cells have surface Ig?

A

No

23
Q

Do plasma cells have high-rate Ig secretion?

A

Yes. primary function is to secrete Abs.

24
Q

Where is IgM primarily found?

A

In the blood

25
Q

Where is IgA primarily found?

A

In mucosal secretions. Also found in serum

26
Q

Where is IgE primarily found?

A

Bound to high-affinity Fc RI receoptor on mast cells in the skin and in the linings of GALT and BALT

27
Q

Define transcytosis.

A

The tarnsport of molecules form one side of an epithelium to the other by endocytosis into vesicles on one side of the ell with release from the other side

28
Q

Define poly-Ig receptor.

A

Receptor on the basolateral surface of epithelial cells that binds to and transports multimeric Igs across the apical surface of the cell

29
Q

Define Brambell receptor.

A

A receptor on the basolateral surface of vascular epithelial cells that binds to and transports IgG from the blood into extracellular spaces.

30
Q

What allows transport of maternal IgG across the placenta to the fetus?

A

Brambell receptors (FcRn)

31
Q

What is passive transfer of immunity?

A

transfer of immunity to a non-immune individual by injection of a specific antibody, immune serum, or T cells. It is used clinically to protect against specific pathogens or toxins.

32
Q

What is natural passive immunity?

A

maternal Abs transferrred to fetus via placental transfer IgG or to newborn via colostrum/breast-milk (IgA)

33
Q

At birth, what type of Abs are present?

A

Essentially the same concentration and makeup of IgG the mother has, due to natural passive immunity. Protects for first 6-9 months of life.

34
Q

What is first antibody made by all B cells? What type Ab will be first to be produced in infant?

A

IgM

35
Q

What type of cell causes the most intense inflammatory response in the body?

A

Mast cells when they release their contents

36
Q

What type of cell helps to kill multicellular parasites?

A

eosinophils.

37
Q

What are B1 B cells?

A

subset of B cells that has a very limited receptor repertoire, and specialize in recognizing things like cell wall polysaccharides. They are the primary cell that responds to TI-2 antigens. Not present until 4-5 years of age.

38
Q

Can infants respond to TD antigens (T cell dependent) and TI-1 antigens?

A

Yes. They have the cell types necessary to do this. T helper cells and B cells (they still lack B1-B cells though)

39
Q

Is there affinity maturation in TI antigen response?

A

No. affinity maturation is a T cell dependent process and TI (T cell independent antigens) do no involve T cells.

40
Q

Is there cell class switching in TI antigen response?

A

No. class switching is a T cell dependent process involved in affinity maturation and TI (T cell independent antigens) do no involve T cells.

41
Q

Where do class switching and affinity maturation take place?

A

in germinal centers in secondary lymphoid tissue

42
Q

What are the differences between folicular dendritic cells and normal dendritic cells?

A

follicular dendritic cells are not APCs. They instead migrate into germinal centers and trap antigens. B cells undergoing class switching will compete for binding with the trapped antigens and those that have the highest affinity are provided survival signals.

43
Q

Where do most plasma cells move to after differentiating? What type of Ig would a plasma cell that migrated to secondary lymphoid tissue lining the GI tract or respiratory tract produce?

A

bone marrow. The exception to this are plasma cells that produce IgA and migrate to secondary lymphoid tissue in GI or respiratory tract

44
Q

Where is IgG primarily found?

A

extracellular spaces and in serum

45
Q

Where do secretory components that are sometimes found on IgA or IgM come from?

A

Poly-Ig receptors, when they help the Ig molecule across a mucosal surface.

46
Q

What receptor allows transfer of maternal IgG to fetuses?

A

the Brambell Receptor (FcRn)

47
Q

Which Ig molecule can pass through breast milk to an infant?

A

IgA

48
Q

Which Ig molecule can pass through the placenta to a fetus?

A

IgG via FcRn (Brambell Receptor)

49
Q

At what age do children’s immune system achieve full functionality?

A

5-6 years

49
Q

What does Fc-E-RI do?

A

It is a receptor on mast cells that binds to IgE with high affinity and allows them to use IgE as antigen-specific receptors.

50
Q

What does Fc-gamma-RIII do?

A

receptor found on NK cells important for ADCC

Note: they can only bind to antibodies that have bound to their antigen

51
Q

What does opsonization mean?

A

making something easier for macrophages to endocytose

52
Q

What type of Ig molecules do eosinophils use as receptors to attack multicellular organisms?

A

IgE, Many eosinophils will form a boundary around the invading organism

KN-Immunology Block 1 (12 decks)

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