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Immunity > B Cells > Flashcards

B Cells Flashcards

1
Q

Membrane bound antibody or surface immunoglobulin

A

B Cell Receptor

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2
Q

Each B cell expresses only one

A

BCR

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3
Q

Many bacteria that cause infections in humans replicate in the

A

Extracellular spaces of the body

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4
Q

Causes the destruction of extracellular pathogens and prevent the spread of intracellular infections

A

Humoral immune response

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5
Q

The humoral immune response functions by the production of antibodies by

A

B cells

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6
Q

Antibodies destroy pathogens and prevent the spread of intracellular infections in which 4 main ways?

A
  1. ) Neutralization
  2. ) Opsonization
  3. ) ADCC (antibody dependent cytotoxicity)
  4. ) Complement activation
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7
Q

Neutralize these agents, opsonize them for phagocytosis, sensitize them for antibody-dependent cellular cytotoxicity, and activate the complement system

A

Antibodies

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8
Q

Blocks binding of microbe and infection of cell

A

Antibody

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9
Q

Antibodies block the infection of the

A

Adjacent cell

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10
Q

Antibodies block the binding of toxin to its

A

Cellular receptor

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11
Q

Opsinization of the microbe by IgG leads to binding of the opsinized microbes to

A

Phagocyte Fc receptors

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12
Q

The Fc receptors activate the

-leads to ingestion and death of microbe

A

Phagocyte

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13
Q

The overall goal of B-cell development is to generate a B cell with

A

BCR on the surface

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14
Q

Bone marrow stromal cells provide signals that are critical for developing

A

B cells

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15
Q

Ig (or V(D)J) recombination provides diversity by generating many different

A

BCRs

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16
Q

However, this is “dangerous” as it often results in unsuccessful

A

Rearrangements

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17
Q

Tonic signaling via the correctly assembled BCR keeps B cells alive and indicates

A

Productive rearrangement

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18
Q

The first checkpoint occurs in the

A

preBCR

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19
Q

The second checkpoint is checking for proper

A

L chain rearrangement

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20
Q

Must be purged from the repertoire

A

Autoreactive B cells

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21
Q

Immature BCR repertoire selected by random recombination. Thus, much of the BCR repertoire is potentially

A

Self-reactive (leading to autoimmunity)

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22
Q

The autoreactive B cells must be

A

Eliminated or inactivated

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23
Q

This is called central tolerance because it occurs in a central lymphoid organ known as the

A

Bone marrow

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24
Q

Auto-reactive B cells that escape this process in the bone marrow are eliminated in the periphery by a process called

A

Peripheral tolerance

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25
Q

What percentage of B cells actually make it and survive?

A

5%

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26
Q

During B cell production, if the B cell is self-reactive, we see receptor editing. What happens if the new receptor is

  1. ) Still self-reactive?
  2. ) No longer self-reactive?
A
  1. ) Apoptosis

2. ) B cell matures

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27
Q

Mature B cells that recognize high affinity self Ag in peripheral tissues in the absence of specific helper T cells may be rendered

-also may die by apoptosis

A

Functionally unresponsive (anergy)

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28
Q

Occurs when helper T cells that are specific for self Ag which then allows self reactive B cells to escape these mechanisms

A

Autoimmunity

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29
Q

Humoral immune response is initiated when B cells bind

A

Cognate antigen

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30
Q

There are two types of antigenic B cell responses. What are they?

A
  1. ) B cell responses to Protein antigens

2. ) B cell responses to Microbial constitutes

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31
Q

B cell responses to protein antigens requires

A

T cell help

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32
Q

These antigens are unable to induce antibody responses in humans or mice that lack

A

T cells

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33
Q

Thus, these antigens are known as

A

Thymus dependent (or T-dependent) antigens

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34
Q

B cell responses to MICROBIOAL CONSTITUTES (like bacterial polysaccharides) antigens do not require

A

T cell help

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35
Q

The antigens are known as

A

T-independent

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36
Q

B cell activation (T-dependent or T-independent) requires

A

Two signals

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37
Q

The first signal is cross-linking of the

A

BCR

38
Q

Activation requires BCR cross-linking. When we have a polyvalent antigen (contains more than one copy of the specific antigenic epitope) this can happen

A

Directly

39
Q

In case of monovalent antigen, antigen is “presented” to B cell by an

A

APC

40
Q

Can help mediate B cell activation

A

Complement

41
Q

Causes increased survival and proliferation of B cells

A

B cell activation

42
Q

B cell activation results in increased expression of

A

B7-1 and B7-2

43
Q

B cell activation results in increased expression of

A

Cytokine receptors

44
Q

B cell activation also results in the increased expression of CCR7 and migration from follicle to

A

T cell areas

45
Q

B cell activation (T-dependent or T-independent) requires two signals (just like T cells). What is signal 2 in

  1. ) T-dependent?
  2. ) T-independent?
A
  1. ) CD40 (B cell) and CD40L (T cell)

2. ) TLR activation

46
Q

In signal 2, interaction between B cell and T cell is mediated by

A

MHC class II antigen presentation

47
Q

This provides specificity to the

A

Immune response

48
Q

Thus, we only get B cell activation when you have T cell specific for the same

A

Antigen

49
Q

Immature B cells mature in the

A

Periphery (spleen)

50
Q

Make IgM that normally circulates in the blood called natural antibodies

A

B1 B-cells

51
Q

These antibodies are highly cross reactive and bind with low affinity to

A

Microbial antigens

52
Q

Produce most of antibodies that mediate adaptive immune responses

A

Follicular B cells

53
Q

Reside in the marginal sinus of the white pulp in the spleen

A

Marginal zone B cells

54
Q

Data suggests a role in defense against bacteria that penetrate the blood stream

A

Marginal Zone B cells

55
Q

Have restricted BCR diversity that might recognize common bacterial antigens and contribute to the very early phase of the adaptive immune response

A

Marginal Zone B cells

56
Q

T-dependent and T-independent immune responses are mediated by different subtypes of

A

B cells

57
Q

Recirculating cells that receive T cell help when they respond to protein antigens and thus initiate T-dependent antibody responses

A

Follicular B cells

58
Q

These responses can lead to the formation of germinal centers, where class switching and somatic mutation of antibody gene occur, resulting in specialized high-affinity

A

Antibody responses

59
Q

T-independent responses to multivalent antigens such as lipids, polysaccharides, and nucleic acids are mediated mainly by

A

Marginal zone B cells in the spleen and B-1 cells in mucosal sites

60
Q

The activation of B cells is initiated by specific recognition of antigens by the surface Ig receptors of the

A

Cells

61
Q

Antigen and other stimuli, including helper T cells, stimulate the proliferation and differentiation of the specific

A

B cell clones

62
Q

Progeny of the clone may produce IgM or other Ig isotypes (e.g., IgG), may undergo affinity maturation, or may persist as

A

Memory Cells

63
Q

Second phase of immune response occurs when activated B cells traffic into lymphoid follicles and form

A

Germinal Centers

64
Q

Immune responses are initiated by the recognition of antigens by

A

B cells and Helper T cells

65
Q

The activated lymphocytes migrate toward one another and interact, resulting in B cell

A

Proliferation and differentiation

66
Q

Restimulationof B cells by helper T cells in extrafollicular sites leads to early isotype

A

Switching

67
Q

The late events occur in germinal centers and include somatic mutation and the selection of high-affinity cells. This is called

A

Affinity maturation

68
Q

B cells and T cells recognize the same

A

Antigen

69
Q

Provides important check point for the initiation of

A

Germinal center response

70
Q

Activated helper T cells that migrate toward the B cell zone express

A

CD40L

71
Q

Their T cell receptors recognize peptide-class II MHC complexes on B cells that have been triggered by antigen and have in turn migrated to the interface between

A

T and B cell zones

72
Q

CD40L on the activated T helper cell then binds to

A

CD40 on B cell

73
Q

This initiates B cell

A

Proliferation and differentiation

74
Q

Bind to cytokine receptors on the B cells and also stimulate B cell responses

A

Cytokines

75
Q

What are the two main outcomes of the germinal center response (T-dependent antigens)

A
  1. ) Affinity maturation

2. ) Isotope switching

76
Q

B cells that have been activated by T helper cells at the edge of a primary follicle migrate into the follicle and proliferate, forming the dark zone of the

A

Germinal center

77
Q

Germinal center B cells undergo extensive

A

Isotope switching

78
Q

Somatic hypermutation of Ig V genes occur in these

A

B cells

79
Q

These B cells then migrate into the light zone, where they encounter follicular dendritic cells displaying antigen and

A

TFH cells

80
Q

B cells with the highest affinity Ig receptors are selected to survive, and they differentiate into

A

Antibody secreting or memory B cells

81
Q

The antibody-secreting cells leave and reside in the bone marrow as long-lived

A

Plasma Cells

82
Q

Early in the immune response, low-affinity antibodies are produced. During the germinal center reaction, somatic mutation of Ig V genes and selection of mutated B cells with high-affinity antigen receptors result in the production of antibodies with

A

High antigen affinity

83
Q

Antigen is limiting in GC, thus only B cells with high affinity BCR specific for antigen will be able to

A

Survive and function

84
Q

Only B cells with high affinity BCR specific for antigen will be able to take up sufficient

A

Antigen from follicular DC

85
Q

Binding of the B cells to antigen displayed on follicular dendritic cells is necessary to rescue the B cells from

A

Programmed Cell Death

86
Q

Isotope switching requires

A

AID (Activation Induced Deaminase) and CD40 ligation on B-cell

87
Q

B cells activated by helper T cell signals (CD40L, cytokines) undergo switching to different

A

Ig isotopes

88
Q

The activation of B cells is initiated by specific recognition of

A

Antigens

89
Q

Naive B cells are stimulated by antigen, become activated, and differentiate into antibody-secreting cells that produce antibodies specific for the eliciting antigen in a

A

Primary immune response

90
Q

Antigen is limiting in GC, thus only B cells with high affinity BCR specific for antigen will be able to process and present the antigen in the context of

A

MHC II

91
Q

Only B cells with high affinity BCR specific for antigen will be able to efficiently interact with

A

T follicular helper cells

92
Q

Only B cells with high affinity BCR specific for antigen will be able to receive signals from T cells that allow high affinity

A

B cell survival

Immunity (33 decks)

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