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Miller- Immunology > Antibody structure > Flashcards

Antibody structure Flashcards

1
Q

What is an antibody?

A

secreted form of the immunoglobulin produced by a B cell.

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2
Q

What are immunoglobulins?

A

antigen-binding molecules of B cells

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3
Q

Antibody molecules are identical to the ______ component of the B cell receptor

A

immunoglobulin

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4
Q

What are antibodies produced by?

A

plasma cells

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5
Q

T or F: each antibody produced by a single B cell has the exact same specificity for antigen

A

true

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6
Q

What is the clonal hypothesis?

A

There is an enormous repertoire of B cells that are produced in bone marrow- each B cell displays many copies of the same BCR on its surface.
During infection, lymphocytes with receptors that recognize the pathogen are activated and proliferate.

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7
Q

A stimulated B cell gives rise to ____.

A

antibody-secreting plasma cells

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8
Q

What is the basic structure of antibody molecules?

A

two identical copies of a heavy chain

two identical copes of a light chain

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9
Q

Describe the regions of an antibody.

A

Variable region- area that recognizes antigens

Constant region- very few differences

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10
Q

What stabilizes immunoglobulin domains?

A

disulfide bonds

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11
Q

What binds the light chains to the heavy chains?

A

disulfide bond

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12
Q

What is the Fc receptor?

A

receptors found on different phagocytes that can recognize different antibody isotypes
Also where complement binds

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13
Q

What are structural characteristics of the light-chain V domain?

A

Made of alternating beta sheets
Beta-barrel arrangement is stabilized by interchain disulfide bond.
Sequence of beta-chain is almost always the same

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14
Q

Where does most variability of light chains exist?

A

loop regions (hypervariable regions)

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15
Q

Structural characteristics of light-chain C domain?

A

Beta-sheets.
Interchain disulfide bond.
Sequence is constant, loops mostly constant

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16
Q

How many hypervariable regions are there in light chains?

A

3 (1,2, and 3)

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17
Q

What are hypervariable regions separated by?

A

framework regions (1-4)

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18
Q

What do framework regions encode?

A

alternating beta sheets of light chain molecule

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19
Q

What is an antigen?

A

any molecule that is bound by an antibody or a T cell receptor

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20
Q

What is an epitope or antigenic determinant?

A

portion of an antigen that is bound by antibody molecule

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21
Q

Antibody binding is _____ and _____.

A

non-covalent and reversible

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22
Q

What is antibody binding mediated by?

A

electrostatic forces
hydrophobic interactions
van der waals forces
hydrogen-bonding

23
Q

What is affinity?

A

binding strength

24
Q

Antibodies have (few/many?) restrictions with respect to binding.

A

few

25
Q

What can antibodies bind to?

A

Native or denatured proteins, peptides

Other types of molecules (carbs, nucleic acids, small molecules, chemicals)

Soluble or particulate antigens.

26
Q

What do T cells (always) recognize?

A

peptides

27
Q

What is a linear epitope? discontinuous epitope?

A

linear- string of amino acids in a row

discontinuous- formed by tertiary structure of protein

28
Q

T cell receptors only recognize ____ epitopes

A

linear

29
Q

What is a multivalent antigen?

A

An antigen with many copies of an epitope or multiple epitopes

30
Q

What are the roles of antibodies?

A

membrane bound: specific antigen receptors for B cells

secreted: bridge btw acquired and innate immune system.

31
Q

What are functions of secreted antibodies?

A

mark microbes or infected cells for destruction by phagocytes (opsonization) or NK cells (antibody-dependent cell-mediated cytotoxicity)
Activates complement pathway

32
Q

What is neutralization?

A

antibodies bind to pathogens and toxins and hinder them from interacting with host cells

33
Q

What is the most abundant isotype?

A

IgG

34
Q

What is the major difference between the subtypes of IgG?

A

the hinge region

35
Q

How many constant and variable regions are in the IgG heavy chain?

A

3 constant, 1 variable

36
Q

What is altered during isotype switching?

A

only the constant region of the heavy chain

37
Q

What do differences in the constant chains of Ab isotypes allow for?

A

versatility of anti-body mediated immune response

38
Q

What is different structurally in IgM and IgE from the other isotypes?

A

Have 4 constant regions and no hinge region

39
Q

IgM is always secreted as a ____

A

multimer (a pentameric form)

40
Q

What are the 5 copies of the immunoglobulin in IgM joined by?

A

J chain

41
Q

Each IgM molecule has (how many?) identical binding domains?

A

10

42
Q

IgA can be secreted as a _______

A

multimer (dimeric most important)

43
Q

What joins dimeric IgA?

A

J chain

44
Q

Which isotype has the longest half-life?

A

IgG

45
Q

Why are serum levels of IgE extremely low?

A

Rapidly bound up by mast cells

46
Q

Which isotype has the highest molecular weight?

A

IgM (b/c it is secreted as a pentamer)

47
Q

Which isotypes are important neutralizers?

A

IgG and IgA

48
Q

Which isotype(s) are important in opsonization?

A

IgG

49
Q

Which isotype functions in sensitization of mast cells?

A

IgE

50
Q

Which isotype is the most efficient activator of complement cascade?

A

IgM

51
Q

Which isotype most efficiently transports across epithelium?

A

IgA

52
Q

Which is the only isotype that transports across the placental barrier?

A

IgG

53
Q

Which isotype is the most important in diffusion into extravascular sites?

A

IgG

54
Q

What are the major functional regions of Abs?

A

Fc regions- binds to complement proteins and Fc receptors

Fab- contains antigen-binding sites (variable region)

Miller- Immunology (1 decks)

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