1 Antibody Structure and Function Flashcards Preview

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Flashcards in 1 Antibody Structure and Function Deck (80):
1

T-F--antigen receptors expressed by adaptive cells recognize a small diversity of antigens?

False--large diversity

2

Does the innate or adaptive immune system use pattern recognition as the infection sensing system?

Innate--receptors are limited and have fixed specificities and recognize only a finite number of microbial products

3

What molecules within B cell receptor complexes mediate antigen recognition and cell activation?

antibody molecules

4

What component dictates the antigen specificity of the BCR?

membrane-bound forms of antibodies component --variable region is key to diversity

5

Does engagement of one BCR complex by antigen lead to activation and the generation of antibodies?

No-multiple complexes engaging signal transduction along with other signals

6

What is the antigen specificity of antibodies determined by in developing B cells?

Gene rearrangement

7

What stage of B cell development rearrange genes encoding antibody components?

B cell progenitors-- [more about this is later lecture]

8

T-f--each B cell clone expresses an antibody with a unique antigen specificity?

True

9

Are there a few different B cell clones produced or many? Why?

Millions
-produce antibodies specific to virtually any antigen

10

coding sequences assembled by gene rearrangement make up what in the BCR complex?

antibody antigen binding sites

11

T-F---antibodies recognize a variety of molecule as antigens?

True---proteins, nucleic acids, carbs, lipids
[NOTE: BROAD SPECIFICITY INCREASES ABILITY TO DETECT AND COMBAT MICROBIAL INFECTIONS]

12

T-F---TCRs can recognize a variety of molecules as antigens?

False---only recognize peptide-MHC complexes as antigens

13

Engagement of the BCR by antigen and activation of B cell leads to the production of what?

soluble antibodies

14

What is the main role of B cells in immune response?

recognize and respond to antigen and produce soluble antibodies?

15

What is the role of antibodies?

seek out and bind to antigens which initiates pathways to remove bound material

16

T-F--- costimulatory signals are not needed in B cell activation?

False

17

Activated B cells proliferate and differentiate into?

antibody secreting cells

18

How do soluble antibodies distribute throughout the body?

passage through bloodstream

19

Antibodies are what shaped molecules?

Y

20

What is the makeup of the main shape of the antibody?

2 identical heavy chains
2 identical light chains

21

What holds the molecules together between anybody chains?

disulfide bonds

22

What do covalently linked carbohydrate chains to heavy chains do?

maintain antibody structure and stability---can influence function of the molecule

23

What are the 2 distinct functional domains of antibodies?

variable[Fab] and constant[Fc]

24

How many variable regions are there in antibodies?

2

25

amino acids in V regions are encoded by ?

randomly joined gene segments

26

T-F--constant region formed by N termini of heavy chains?

False--C-termini

27

What dictates the mulimerization state, anatomic localization and effector function?

Constant region

28

What does Fab stand for?

fragment of antigen binding

29

What does Fc stand for?

fragment crystallizable---form crystals when stored at cold temperatures

30

T-F---at the gene level, V regions are encoded by portions of the heavy and light chain genes that are generated by gene rearrangement?

True

31

T-F---within the V region, the C-termini of the heavy and light chains form a composite surface that mediates antigen binding?

False---it is the n-termini

32

What are segments in V regions that are highly diverse in the A.A. content and mediate direct contact with antigens?

complementarity determining regions (CDRs)

33

How can the antigen affinity of V regions be increased?

somatic mutation
affinity maturation

34

What alters DNA sequences encoding V regions, resulting in AA changes within the antigen binding pocket?

somatic hypermutation

35

What selects for B cell clones expressing antibodies with high affinity for antigen due to somatic hypermutation?

affinity maturation

36

What does high affinity for antigen increase?

stability and duration of antigen-antibody interactions

37

What do C regions dictate?

tissue distribution
multimerization state
antibody effector function

38

How are human antibodies classified?

based on constant regions

39

Where are IgM mostly found?

blood

40

What is the most abundant Ig in body?

IgG-- distributes to blood and tissue

41

Where is IgE mostly found?

little in blood mostly in tissues bound to mast cells

42

Where is IgA mostly found?

some in blood, but mainly secreted across epithelial layers lining respiratory and digestive tracts

43

What Ig is expressed by mature B cells, integrated into BCRs and secreted very little?

IgD

44

What do naive B cells express?

IgM and IgD

45

Antibody secreting cells express?

IgG, IgA or IgE

46

Activated B cells with T cell help will do what to heavy chain?

will recombine DNA encoding the heavy chain

47

T-F---generally, B cells that undergo class switching also undergo somatic hypermutation and affinity maturation

True

48

What antibody is transferred across placenta?

IgG

49

What Ig forms pentamer?

IgM

50

What Ig forms dimers?

IgA

51

Infants receive what Igs from mother?

IgA (breast) and IgG (placenta)

52

What type of bonds holds together antibody dimers and pentamers? Where does the multimerization occurs?

-cysteine bonds with the J chain help
-occurs during transit through ER and Golgi

53

What are the 5 pathways antibodies promote clearance of microbes?

-agglutination
-neutralization
-activation of complement cascades
-Fc Receptor-mediated opsonophagocytosis
-antibody-dependent cytotoxicity

54

What traps microbes in a complex preventing cell-cell contact and colony formation/replication?

agglutination

55

What blocks contacts with host molecules and cells impeding attachment or entry into cells?

agglutination

56

Agglutinated materials are targets for what?

phagocytes

57

What Ig is very effective for agglutination?

IgM--10 antigen sites per pentamer

58

What does antibody neutralization do?

-block interactions with host cell receptors and eventual entry
-prevent toxins from entering cells

59

Neutralized material will eventually…?

be ingested by phagocytes

60

Are monomers better for neutralization?

Yes

61

Antibodies bound to surfaces can be recognized by what component of the complement system?

C1q

62

Antibody-C1q interaction induce a conformation change in the C1 complex…what does this activate?

C1s and C1r proteases

63

What does C1s generate?

C4b and C2a creating classical C3 convertase

64

The C3 converses lead to what deposition?

C3b

65

Deposition of C3b will drive formation of what?

-membrane attack complex--->cell lysis
-macrophage and neutrophil phagocytosis

66

T-f---antibodies alone on the surface can be recognized by Fc receptors expressed on phagocytes?

True---multiple contacts will lead to phagocytosis

67

Can monomeric or soluble antibodies activate cells via Fc receptors?

No

68

T-f---infected cells often express microbial antigens on their surface?

True

69

T-F---NK cells have Fc receptors that can recognize bound antibodies?

True---activation leads to cytotoxic function of NKs
[imporatant for virus or intracellular bacteria]

70

What antibody is critical for early antibody responses and defense against extracellular microbes?

IgM

71

Does IgM have a high or low affinity for antigen?

relatively low

72

Surface bound IgM activates what>

complement pathway cascade

73

Do IgG have a high or low affinity?

High----have a long half-life

74

What are the main differences between IgG subtypes?

-hinge region
-ability to fix complement
-affinity for Fc receptors

75

IgG3, IgG2, IgG4 and IgG1 is ordered in what order for ability to fix complement?

IgG3>IgG1>IgG2>IgG4

76

IgG antibodies can engage 5 of 5 major B cell effector pathways?

false---4 of 5
-complement pathway
-Fc mediated phagocytosis
-neutralization
-Ab dependent cytotoxicity

77

Does IgA have high or low affinity?

generally high

78

How does IgA chiefly function (main effector model)?

neutralization

79

IgE has high or low affinity?

High

80

T-F---IgE bind constitutively to IgE receptor expressed on mast cells

True---multiple IgE antigen contacts leads to activation