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Immunology > Antibody Structure/ Generation of B cell diversity > Flashcards

Antibody Structure/ Generation of B cell diversity Flashcards

1
Q

What are the highly variable recognition molecules of the adaptive immune response?

A

Immunoglobulin (BCR) and T cell receptors

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2
Q

What is active immunity? Passive immunity?

A

Active is generated in the host (infection, vaccine); Passive is generated elsewhere and transferred to host

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3
Q

True or False: Antigen receptors are unique to the adaptive immune response

A

True

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4
Q

What is the basic structure of the TCR?

A

A heterodimer composed of two transmembrane glycoproteins

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5
Q

What is the name of the regions of antigen molecule recognized by the BCR/TCR?

A

Epitopes

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6
Q

What kind of antigens can B cells recognize? T cells?

A

B cells can recognize free, surface bound, or degraded antigen; TCRs only recognize processed antigen peptides presented on an MHC

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7
Q

What is an immunogen?

A

Epitopes that induce an immune response and are recognized by antigen receptors

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8
Q

What are haptens?

A

Small, non-immunogenic, but antigenic molecules

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9
Q

What are the characteristic of an antigen that favor induction of an immune response?

A

Size (>10 kDa), Complexity, conformation (accessible), and chemically cleavable

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10
Q

What confers the different functions in different antibody isotypes?

A

Differences in the Fc region

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11
Q

By what cells are antibodies secreted?

A

Plasma cells

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12
Q

What polypeptides make an antibody?

A

2 identical heavy chains and 2 identical light chains

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13
Q

What domains are contained within the immunoglobulin light chain? Heavy chain?

A

One variable domain and one constant domain; One variable and 3 or 4 constant domains

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14
Q

What makes up the antigen-binding site of immunoglobulins?

A

The combination of the variable domains from one L chain and one H chain

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15
Q

What are the different H chains? L chains?

A

Gamma, mu, delta, alpha, and episilon; kappa and lambda

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16
Q

What is the hinge region of an antibody and what is its importance?

A

The flexible, unstructured portion in the middle of the Ab; allows antigen binding arms to adopt different orientations

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17
Q

What are the two fragments an antibody can be cleaved into by proteases?

A

Fab (fragment antigen binding=arms) and Fc

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18
Q

Where on the antibody are the hypervariable regions? How many are there per variable domain?

A

There are 3 HV per variable domains and they are located on loops at the end of the arm

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19
Q

What are complementarity-determining regions?

A

Hypervariable regions on antibodies

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20
Q

What forms the Ag binding site at the tip of each Fab on an antibody?

A

Pairing of HV regions from the H and L chains

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21
Q

How many total hypervariable regions are their per antibody? How many different HV regions/ antibody?

A

12– 2 identical pairs of 6

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22
Q

What dictates the specificity of an antibody?

A

The different sequences of variable regions which create different antigen binding sites

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23
Q

True or False: An antibody that recognizes one pathogen is also designed to recognize other pathogens

A

False

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24
Q

What is a multivalent antigen?

A

An antigen with more than one epitope

25
Q

What are the different types of epitopes? What is each

A

Linear epitopes (sequential amino acids) and discontinuous epitopes (amino acids brought together via protein folding

26
Q

True or False: Not all 6 complementary determining regions may make contact with an antigen

A

True

27
Q

What is avidity?

A

Combined strength between more than one antigen binding site and more than one epitope

28
Q

What is avidity?

A

Combined strength between more than one antigen binding site and more than one epitope

29
Q

What antibody generally has low affinity but high avidity?

A

IgM

30
Q

What are abzymes?

A

A catalytic antibody; a monoclonal antibody that binds and changes the antigen

31
Q

What are polyclonal antibodies?

A

Antibodies generated from a mixture of different B cells and recognizes multiple epitopes

32
Q

True or False: Humoral immunity response to infection is polyclonal?

A

True

33
Q

How are monoclonal antibodies generated?

A

B-cell hybridomas- b cells fused with tumor cells

34
Q

What is agammaglobulinemia?

A

The absence of antibodies

35
Q

What are chimeric and humanized monoclonal antibodies?

A

Chimeric- mouse variable region + human constant regions; Humanized- mouse CDR replaces human CDR

36
Q

How is diversity of antigen receptors generated?

A

Somatic recombination - Gene rearrangement

37
Q

What segments are in the variable domain?

A

Heavy chains- V(ariable), D(iversity), and J(oining); Light chains- V and J

38
Q

What cells in the body undergo somatic recombination?

A

Only B and T cells

39
Q

True or False: Somatic recombination must occur before the gene can be transcribed?

A

True

40
Q

What is clonal selection and expansion?

A

Clonal selection is the process by which only B and T cell receptors that recognize a given pathogen are activated to proliferate and form clones of cells with identical receptors (clonal expansion)

41
Q

What is the order of rearrangements to make the V region in the Ig heavy chain?

A

D and J and then DJ and V

42
Q

What is V(D)J recombinase?

A

A set of enzyme required for V-D-J?

43
Q

What is the RAG complex?

A

RAG-1 and RAG-2 form a RAG complex which binds to recombination signal sequences and initiates recombination events

44
Q

What is junctional diversity?

A

The RAG compex cleaves RSSs from the D and J (or DJ and V) gene segments to yield DNA hairpins, and then it opens the hairpins generating palindromic P-nucleotides. Terminal deoxynucleotidyltransferase randomly fills in the gaps with non-templated nucleotides (N nucleotides)

45
Q

True or False: Each B cell will produce hundreds of Heavy and Light chain combinations

A

False: only one

46
Q

What kind of Ig is expressed on naive B cells?

A

IgM and IgD

47
Q

What is the mechanism by which both IgM and IgD are expressed on naive B cells?

A

mRNA splicing

48
Q

What confers the difference between surface-Ig and secreted antibodies? What is the mechanism by which Ig changes from surface to secreted?

A

Membrane Ig have hydrophobic tails and secreted have hydrophilic tails; Alternative RNA splicing

49
Q

What is somatic hypermutation?

A

When a B cell undergoes clonal expansion the clones will accumulate small point mutations in the CDR loops and some mutations will increase the affinity

50
Q

What is affinity maturation? What enzyme is required?

A

The process by which the interaction between antibody and epitope improves; Activation-induced cytidine deaminase (AID)

51
Q

True or False: T cells do not undergo somatic hypermutation?

A

True

52
Q

What is the first antibody produced?

A

IgM

53
Q

What is the structure or IgM antibodies?

A

Pentameric– 10 arms total

54
Q

What is the reason for isotype/class switching? What enzyme is required?

A

Production of antibodies with different effector functions but same antigen specificity; AID

55
Q

What is the mechanism of Isotype switching?

A

Rearrangement of VDJ and C genes

56
Q

What factors dictate which isotype is needed?

A

Location and type of infection

57
Q

What stimulates isotype switching?

A

T-cell signals

58
Q

What generates TCR diversity?

A

Somatic recombination through RAG1 and RAG2- V segment joins to J segment in the alpha chain, and D with J and DJ with V in beta chain

59
Q

True or False: RAG is required for generation of diversity of both T and B cells?

A

True

Immunology (13 decks)

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