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Immunology > Antibodies And Antigens > Flashcards

Antibodies And Antigens Flashcards

1
Q

How many polypeptide chains are present in an antibody?

A

Four - two light and two heavy chains.

They are bound by disulfidige bridges and noncovalent interactions.

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2
Q

What region of the antibody is responsible for antigen binding?

A

The variable region

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3
Q

What is the Fab fragment?

A

Fragment Ag-binding

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4
Q

Both the heavy and light chains are divided into V and C regions. What do the V and C regions contain?

A

The V region contains the Ag-binding site and the C region determines the fate of the Ag.

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5
Q

What are the 5 different kinds of H-chains that determine the class of antibody?

A

Mew

Delta

Gamma

Sigma

Alpha

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6
Q

What are the 5 different classes of antibodies?

A

M

E

A

D

G

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7
Q

True or false: each Ab unit can have only a kappa or lambda L chain,b ut not both.

A

True

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8
Q

What are some of the interactions betweenthe H and L chains?

A

Intrachain disulfide bridges.

They create polypeptide loops, domains, of 110 amino acids.

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9
Q

What are the Ig superfamily proteins?

A

A large group of cell surface and soluble proteins that are involved in the recognition, binding or adhesion processes of cells.

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10
Q

What are some members of the Ig superfamily?

A

IgG

CD4 receptor of T cells

CD28

ICAM-1

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11
Q

The Ag-binding sites are formed by the juxtaposition of what two domains?

A

The VL and VH domains.

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12
Q

A membrane bound IgM on a B cell has what?

A

C terminal transmembrane and cytoplasmic portions that anchor the molecule in the plasma membrane.

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13
Q

What is IgG cleaved by?

A

Papain.

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14
Q

What does papain digestion allow for?

A

The separation of two Fab fragments and complement-and Fc receptors binding the Fc fragment.

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15
Q

What does pepsin generate?

A

A single bivalent antigen-binding fragment, F(ab’)

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16
Q

What is the role of hinges in Abs?

A

It allows the antibodies to change how they spread their antigen binding sites.

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17
Q

What is affinity?

A

The tightness of Ag-Ab binding.

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18
Q

The higher the binding constant, the ___ likely the Ab is to dissociate from the Ag.

A

Lower

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19
Q

Abs formed in the primary response soon after the injection of an Ag are generally ___ affinity.

A

Lower

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20
Q

Abs produced by a memory response have ___ affinity than those in a primary respnose.

A

Higher

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21
Q

When is an example of when affinity of an Ab is critical?

A

When the Ag is a toxin or virus and must be neutralized rapidly at low titers.

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22
Q

What is valence?

A

The maximum number of antigenic determinants with which an Ab can react.

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23
Q

IgG contains two Fab regions and can bind two molecules of Ag or two identical sites on the same particle. What is its valence?

A

2

24
Q

What is an advantage of having two or more binding sites for an Ag?

A

It can dramatically increase the tightness of binding of the Ab to Ags.

25
Q

What is avidity?

A

It gives a measure of the overall strength of an Ab-Ag complex. It is dependent on:

Affinity of the Ab for the epitope
Valence of both the Ab and the Ag

26
Q

low affinity IgM can be extremely effective in neutralizing a microorganism. Why is this so?

A

It has a large number of binding sites.

27
Q

When antibodies change from membrane to secreted form, how does their effector function change?

A

They change from a B cell receptor function to effector function.

28
Q

When antibodies undergo isotype switching, how is effector function changed?

A

Each isotype serves a different set of effector functions.

29
Q

When there is affinity maturation in the variable region of an antibody, how is antigen recognition changed?

A

There is increased affinity of antigen recognition.

30
Q

What are IgGs involved in?

A

Phagocytosis

31
Q

What are IgAs involved in?

A

Mucosal defenses

32
Q

What are IgEs involved in?

A

Allergic responses

33
Q

What are IgMs involved in?

A

Complement activation

34
Q

What is the most common Ab in mucosal secretions?

A

IgA

35
Q

What Ab is mainly found in the plasma?

A

IgM

36
Q

What Ab is found on the surface of mast cells?

A

IgE

37
Q

What Ab penetrates deep into the tissue?

A

IgG

38
Q

What is the most abundant Ig in the blood?

A

IgG

39
Q

What Ig provides the bulk of immunity to most bloodborne pathogens?

A

IgG

40
Q

What is the only Ab class that can cross the placenta to provide passive humoral immunity to the developing fetus and to the infant on its birth?

A

IgG

41
Q

What is the function of FCRn (receptor for Fc regions)?

A

It transfers maternal IgG to the fetal circulation.

This will provide important protection prior to the generation of immunocompetence in the fetus.

42
Q

What is the primary function of IgD?

A

It is an Ag receptor on B lymphocytes and is also involved in regulating B cell function when it encounters Ag.

43
Q

Naive B cells can express what two Igs?

A

IgM and IgD.

Both are specific for the same Ag.

44
Q

When IgM and IgD are expressed on a B cell, what happens to the Ag?

A

The Ag is internalized, processed and presented to helper T cells.

45
Q

What is the fate of Ag activated B cells?

A

They proliferate and differentiate into plasma cells, thus initiating the developmentof a humoral immune response.

46
Q

What is the first Ab produced by any Ag-activated B cell prior to contact with T helper cells?

A

IgM

47
Q

What is an important role of IgM?

A

It plays a critical role in defense before sufficient quantities of IgG have been synthesized.

48
Q

Where is IgM primarily found?

A

In the bloodstream

49
Q

The overall avidity of an IgM is ___, making IgM very effective in the removal of the microbe.

A

High

50
Q

What is the major Ig present in the colostrum, milk and saliva?

A

IgA

51
Q

What are two unique polypeptide chains of IgA?

A

Secretory component (SC)

J-chain (joining chain)

The SC component is responsible for stabilizing IgA against proteolytic degradation in the GI tract.

52
Q

How are the two Ig units comprising the secretory IgA held together?

A

By the J-chain through disulfide bridges.

53
Q

Which Ig is is a major defense mechaism against microbial invaders at mucosal surfaces?

A

IgA

54
Q

What Ig is present at low levels in the serum?

A

IgE

55
Q

What does IgE play a signficiant role in?

A

Enhancing acute inflammation, in protection from infection by worms and in allergic reactions.

56
Q

What type of cells does IgE bind to?

A

Receptors on mast cells.

57
Q

What are effector properties of Abs?

A

Immunomodulation

Direct antibacterial activity

Toxin neutralization

Activation of complement

Opsonization

Organized T-cell response

Reduced damage to host from inflammatory response

Immunology (17 decks)

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