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I&I - M1T1 > Humoral Immunity > Flashcards

Humoral Immunity Flashcards

1
Q

What receptor is expressed on B cells that recognizes complement bound to a microbe?

A

CD21 (Complement Receptor 2 - CR2), which binds to C3d

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2
Q

Production of what antibody is considered a T-independent response?

A

IgM

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3
Q

What are the light Ig chains?

A

kappa & lambda

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4
Q

How does avidity differ from affinity?

A

Affinity refers to the strength of an individual interaction between an epitope and an antigen-binding site. Avidity refers to the sum of all interactions between antibodies and antigens.

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5
Q

What is affinity maturation? How does it take place?

A

Affinity maturation is the process of producing antibodies with greater affinity for an antigen. This process takes place via somatic hypermutation, which is point mutations in the variable region of an antibody. No recombination takes place.

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6
Q

What is the first antibody secreted by an activated B cell?

A

IgM

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7
Q

When will IgE production be increased?

A

Infection with parasites, allergic response, asthma

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8
Q

B cells being producing antibodies in the extrafollicular region. Is this the primary site of the humoral response?

A

No, the humoral response is fully developed in the germinal center of the lymph nodule. This is where proliferation, isotype switching, affinity maturation, and memory takes place.

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9
Q

What is essential for the activation of a B cell by a T cell?

A

CD40-CD40L binding

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10
Q

What may serve as the second signal for B cell activation?

A

Complement and PAMPs

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11
Q

What antibody can cross the placenta and provides immunity for the fetus?

A

IgG

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12
Q

Describe the process of a T-dependent B cell activation.

A

A B cell recognizes an antigen and undergoes receptor-mediated endocytosis. The antigen is processed and displayed on MHC II. The B cell moves from the follicular zone to the T cell zone following cytokines.

Simultaneously, an activated T cell moves toward the follicular zone, produces cytokines, and displays CD40 ligand on its surface.

The B and T cell interact. Binding of CD40 on the B cell with CD40L on the T cell activates the B cell to undergo isotype switching and affinity maturation,

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13
Q

What name is given to B & T cells that have never encountered an antigen?

A

Naive B & T cells

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14
Q

Release of TGF-B will result in isotype switching to which antibody isotype?

A

IgA

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15
Q

What is antibody dependent cellular cytotoxicity?

A

This refers to the ability of antibodies to bind host cells that do not display MHC I. This enables NK cells to phagocytize and degrade the cell.

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16
Q

What term describes the ability of antibody monomers to bind determinants that are far from one another?

A

Flexibility

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17
Q

What are the heavy Ig chains?

A

IgM, IgA, IgG, IgD, IgE

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18
Q

What antibody has the longest half-life, is most abundant in the blood, and is able to carry out all major functions of antibodies?

A

IgG

19
Q

How do B cells in the follicle encounter antigens?

A

Antigens are delivered to B cells via afferent lymphatics from tissues. Larger antigens may also be presented to B cells from macrophages in the subcapsular sinus and smaller antigens may diffuse directly into the sinus.

20
Q

What is the name given to an antibody-secreting B cell?

A

Plasma cell

21
Q

True/False. B Cells require two signals for activation.

A

True. The first signal is antigen binding to the B cell. The second signal is produced by the innate immune system in response to the invading microbe. Both signals must be present in order for the B cell to activate.

22
Q

IgM has a greater avidity than IgG. Why is this?

A

IgM exists in a pentamer form when secreted. As a result, the antibody can bind with more antigens than IgG, which exists only as a monmer.

23
Q

Where are most B cells located? What are these cells called?

A

Follicular B Cells - lymphoid follicles of the spleen and lymph nodes

24
Q

What are the general functions of antibodies?

A

Neutralize toxins and microbes; Opsonizize and phagocytize microbes; cellular cytotoxicity; complement activation

25
Q

Release of IFN gamma will result in switching to which antibody isotype?

A

IgG

26
Q

What cytokine must be expressed for isotype switching to IgE?

A

IL-4

27
Q

True/False. Memory B cells secrete antibodies that provide extended protection.

A

False. Memory B cells are long-lived and circulate in the blood and tissues, but do not secrete antibodies. Long-lived plasma cells produce antibodies and maintain high IgG following an infection.

28
Q

What name is given to activated and differentiated B & T cells?

A

Effector B & T cells

29
Q

IgA provides significant protection in what parts of the body?

A

Mucosal linings

30
Q

What is the function of IgG?

A

Opsonization and phagocytosis, complement activation

31
Q

How do antibodies support phagocytosis of pathogens?

A

The Fab region of the Ig binds the microbe. The Fc region is then capable of binding and activating phagocytes.

32
Q

What interaction between antigen presenting cells and Helper T cells results in activation of the T cell?

A

Through the binding of B7 on the APC with CD28 on the Helper T cell.

33
Q

What term describes the proliferation of an activated B cell to produce more cells that recognize the antigen?

A

Clonal selection

34
Q

IgG has 4 isoforms. What form(s) are responsible for activating the complement system?

A

IgG1 & IgG3

35
Q

What are the consequences of B cell activation by an antigen?

A

B cell survival & proliferation; antibody secretion; migration from the follicle to the T cell zone for interaction with Helper T cells

36
Q

What enables IgG to cross the placenta and provide fetal protection?

A

Binding of IgG to the neonatal Fc receptor (FcRn)

37
Q

What antibody is passed from mother to neonate through breast milk?

A

IgA

38
Q

What enzyme is responsible for isotype switching in antibodies?

A

AID - Activation Induced Cytidine Deaminase

39
Q

What is the result of T-dependent B cell activation?

A

Production of different antibodies with different heavy chains & antibodies with higher affinity for the antigen

40
Q

What antigens do B cells recognize? How do they vary in immunogenicity?

A

Proteins > Polysaccharides > Lipids > Nucleic Acids

41
Q

To which cells does IgE bind?

A

Mast cells, basophils, eosinophils

42
Q

How does the structure of IgM change after being released from a B cell?

A

When attached to the B cell, IgM exists as a monomer. When released and circulating, IgM is a pentamer than can activate the classical complement pathway.

43
Q

What is antibody dependent cellular cytotoxicity?

A

This refers to the ability of antibodies to bind host cells that do not display MHC I. This enables NK cells to phagocytize and degrade the cell.

44
Q

What are the only types of antigens recognized by T cells?

A

Polysaccharide antigens. All other antigen types are recognized by B cells

I&I - M1T1 (36 decks)

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