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Immunology > Lecture 14 (Exam 2) > Flashcards

Lecture 14 (Exam 2) Flashcards

1
Q

Mature Ag-responsive B cells develop from ______ ______ precursors in the absence of Ag.

A

Bone marrow

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2
Q

Humoral immune responses are initiated by the recognition of Ags by specific _____ on B lymphocytes.

A

BCR

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3
Q

Ag activates mature NAIVE B cells by binding to membrane _____ and _____ on these cells.

A

IgM

IgD

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4
Q

A single B cell may give rise to as many as _____ Ab-secreting cells per week.

A

5,000

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5
Q

At the peak of humoral immune response, about 10(12) Abs are produced every (WEEK/DAY).

A

Day

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6
Q

The activation of B cells is initiated by specific recognition of ____ by the surface BCRs.

A

Ags

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7
Q

Ags and other stimuli, including _______ cells, stimulate the proliferation and differentiation of the specific B cell clone.

A

T helper

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8
Q

The progeny of the B cell clone may differentiate into plasma cells that produce –

1) _____
2) Other Ig isotypes (i.e., IgG)
3) Undergo ______ ______
4) ______ cells

A

IgM
Affinity maturation
Memory

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9
Q

Primary and secondary Ab responses to _______ Ags differ qualitatively and quantitatively.

A

Protein

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10
Q

In a (PRIMARY/SECONDARY) immune response, naive B cells are stimulated by Ag, become activated, and differentiate into Ab-secreting cells that produce Abs. _____ > _____ specific for the eliciting Ag.

A

Primary
IgM
IgG

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11
Q

A (PRIMARY/SECONDARY) immune response is elicited when the same Ag stimulates _______ B cells, leading to production of Abs (_____ > ______).

A

Secondary
IgG
IgM

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12
Q

Secondary response is characterized by –

– More ______ production of Abs than was produced in the primary response.

– ______ amounts of Abs produced as compared to the primary response.

– _______ _______ of the heavy chain.

– _______ _______ Ag-Ab binding.

A

Rapid
Larger
Isotype switching
Affinity maturation

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13
Q

B cell responses are divided on _______ and _______.

A

T-dependent (TD)

T-independent (TI)

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14
Q

Ab responses to multivalent non-protein Ags with repeating epitopes, such as polysaccharides, some lipids, and nucleic acids, do not require Ag-specific helper T lymphocytes. Multivalent Ags are called _______ Ags.

A

TI (T-independent)

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15
Q

TI responses are elicited by engagement of _____ and may be potentiated by the signals from other receptors on the B cells.

A

BCR

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16
Q

In contrast, Ab responses to protein Ags require participation (help) of CD4+ T helper lymphocytes. Therefore, proteins are classified as _______ Ags.

A

TD (T-dependent)

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17
Q

A specialized type of helper T cell, called a ________ helper T cell, facilitates the formation of _______ ______ where activated B cells proliferate.

A 
Follicular 
Germinal centers (GCs)
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18
Q

Follicular B-2 cells respond to protein Ags and thus initiate _______ Ab responses.

A

T-dependent

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19
Q

Marginal zone B cells respond to multivalent Ags and are ________.

A

T-independent

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20
Q

B-1 cells in mucosal sites also respond to multivalent Ags and are ________.

A

T-independent

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21
Q

The (B-1/B-2) B cells arise from the fetal liver by the eighth gestational week. These cells might represent a transitional type of lymphocyte that bridges the innate and adaptive immune systems. They are T-independent.

A

B-1

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22
Q

The B-1 B cell repertoire is quite limited in comparison to that of _____ cells.

A

B-2

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23
Q

B-1 B cell _____ are often directed against conserved microbial Ags.

A

Abs

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24
Q

Conventional B cells, which are _____ B cells, are widely distributed throughout the body. These cells are continually replaced from the bone marrow throughout adult life and require interaction with T cells for their activation and proliferation (T-dependent).

A

B-2

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25
Q

To initiate Ab responses, Ags have to be transported to the B cell areas of the _____ and _____.

A

LNs

Spleen

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26
Q

Most mature naive B lymphocytes are ________ B cells which are also called recirculating B cells or _____ cells.

A

Follicular

B-2

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27
Q

Follicular B cells constantly recirculate in the blood from one to another secondary lymphoid organ, which are…

A

Spleen
Lymph nodes
Mucosal lymphoid tissues

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28
Q

In the secondary lymphoid organs, follicular B cells migrate into the B cell zones of these tissues called _______.

A

Follicles

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29
Q

The ______ chemokine secreted by resident follicular DCs (FDCs are not DCs coming from tissues) guides the movement of B cells.

A

CXCL13

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30
Q

CXCL13 attracts naive B cells into the _______.

A

Follicles

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31
Q

The Ag that is presented to B cells is generally in its intact, native conformation and is not processed _____.

A

APCs

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32
Q

T/F. Ag may be delivered to naive B cells in lymphoid organs in different forms and by multiple routes.

A

True

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33
Q

Most Ags from tissue sites are transported to lymph nodes by _______ _______ _______ that drain into the _________ ________ of the LNs.

A

Afferent lymphatic vessels

Subcapsular sinus

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34
Q

_______ Ags (generally smaller than 70 kD) may reach the B cell zone of the follicle and interact directly with B cells.

A

Soluble

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35
Q

_______ Ags may be captured by resident FDCs and transported into follicles, where they can activate B cells.

A

Large

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36
Q

Microbes and Ag-Ab complexes are captured by subcapsular sinus _________ which deliver Ags to follicles.

A

Macrophages

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37
Q

FDCs play a central role in the (INNATE/ADAPTIVE) immune response.

A

Adaptive

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38
Q

As a major stroll cell constituent of follicles, FDCs secrete _______ to organize the intra-follicular migration of B cells and T-FH cells (follicular T helper cells).

A

CXCL13

39
Q

FDCs have the unique capacity to retain immune Ag-Ab complexes on their surface for long periods (week to month). Ags retention by FDCs is mediated by ________, _____ or _____ complement receptors. These immune complexes play a key role during the germinal center reaction, as they provide the antigenic substrate that drives antibody _______ _______.

A

FcyRIIb (Fc receptors)
CR1
CR2 (CD21)
Affinity maturation

40
Q

FDCs do NOT express ________, and they do NOT phagocytose and process exogenous Ags for ________.

A

Class II MHC

Class II MHC

41
Q

Follicular B cell survival depends on signals from the BCR as well as on inputs received from cytokine called _______.

A

BAFF (B cell-activating factor of the TNF family)

42
Q

BAFF provides maturation and survivor signals through the _______ _______.

A

BAFF receptor

43
Q

BAFF is mainly produced by _______ cells in lymphoid follicles and in the bone marrow.

A

Myeloid

44
Q

The BCR signaling (1) initiates the process of B cell activation. At the same time, the BCR (2) internalizes the bound Ag into eadosomal vesicles. If the Ag is a _______, it is processed and presented (class II MHC) on the B cell surface for recognition by T helper cells.

A

Protein

45
Q

B cell activation is facilitated by the _____/_____ coreceptor on B cells. Activation of B cells through the BCR may be enhanced by complement-coated Ags that can ligate both the BCR and _____.

A

CR2/CD21

CR2

46
Q

Simultaneous _______ recognition and TLRs signaling may contribute to B cell activation.

A

PAMPs

47
Q

Some non-microbial polysaccharides also activate complement, and this is one reason that such Ags are able to induce Ab responses without ______ help.

A

T cell

48
Q

Protein Ags recognized by membrane Ig are endocytose and processed, and peptide fragments are presented in association with ________ molecules.

A

Class II MHC

49
Q

_______ cells recognize MHC-peptide complexes on the B cells and then stimulate B cell responses.

A

Helper T

50
Q

In responses to _______-_______ conjugates, the _______ (the B cell epitope) is recognized by a specific B cell, the conjugate is endocytose, the carrier protein is processed in the B cell, and peptides from the carrier (the T cell epitopes) are presented to the helper T cell.

A

Hapten-carrier

Hapten

51
Q

When helper T cells are activated by recognizing Ags presented by B cells, they initiate the expression of ______.

A

CD40L

52
Q

CD40L binds to ______ on B cells and stimulates B cell proliferation and differentiation.

A

CD40

53
Q

_________ produced by the helper T cells also contribute to B cell responses.

A

Cytokines

54
Q

Immune responses are initiated by the recognition of _____ by B cells and CD4+ T cells.

A

Ags

55
Q

The activated lymphocytes migrate toward one another and interact causing B cell _________ and ________.

A

Proliferation

Differentiation

56
Q

B-T interaction leads to minimal isotype switching and generation of short-lived plasma cells mainly producing _____ (some may produce _____ having relatively low affinity).

A

IgM

IgG

57
Q

B cells migrate into the ________ ________ and undergo (a) somatic mutation, (b) affinity maturation, (c) isotype switching, generation memory B cell and long-lived plasma cells producing either IgG, IgA, IgM, or IgE.

A

Germinal centers

58
Q

The _______ is a diffuse system of small concentrations of lymphoid tissue found in various submucosal membrane sites of the body such as GI tract, oral passage, nasopharyngeal tract, lung, etc.

A

MALT (Mucosa-associated lymphoid tissue)

59
Q

The generation of _____ cells requires sequential activation of T cells, first by DCs and then by activated B cells. The ______ cells migrate into germinal centers, where they activate B cells.

A

T-FH (Follicular helper T cell)

T-FH

60
Q

_______ is a receptor for CXCL13, and mediates migration in the B cell zone.

A

CXCR5

61
Q

______ is secreted by T-FH cells and it is required for GC development and generation of plasma cells.

A

IL-21

62
Q

T-FH cells secrete cytokine(s) ______, ______, or ______ which control Ab isotype switching.

A

IFN-y
IL-4
TGF-B

63
Q

Within 4 to 7 days after Ag exposure, activated Ag-specific B cells induce some previously activated T cells to differentiate into _______ cells.

A

T-FH

64
Q

______ cells have a unique phenotype that makes them distinct from the Th1, Th2, Treg, and Th17 subsets of effector T cells.

A

T-FH

65
Q

T-FH cells are drawn into lymphoid follicles by _______ and play a critical role in GC formation and function.

A

CXCL13

66
Q

T-FH cells express ______, ______, the cytokine ______, and the transcription repressor ______.

A

ICOS (Inducible costimulator)
PD-1 (Programmed death-1)
IL-21
Bcl-6

67
Q

T-FH plays several roles in the activation and differentiation of B cells in the GC reactions that involves ______, ______, and _____ on B cells.

A

ICOSL
CD40L
IL-21R

68
Q

Cytokine ______ is important for the generation of B cell responses in germinal centers resulting in development of B cells, isotype switching, affinity maturation, and antibody production.

A

IL-21

69
Q

The GC can be divided into three zones, which are…

A

Dark zone
Light zone
Mantle zone

70
Q

Activated B cells migrate into the follicle and proliferate, forming the _____ zone of the germinal center. These B cells undergo extensive isotype switching and somatic hypermutation of Ig V genes.

A

Dark

71
Q

B cells migrate into the ______ zone, where they encounter follicular DCs displaying Ags and T-FH cells.

A

Light

72
Q

B cells with the highest affinity Ig receptors receive “tonic signal” to survive, and they proceed for the positive/negative selection or ______ editing.

A

BCR

73
Q

Positively selected B cells differentiate into Ab-secreting cells and _______ B cells.

A

Memory

74
Q

The Ab-secreting cells leave the GC and reside in the bone marrow as long-lived _______ cells, and the memory B cells enter the recirculating lymphocyte pool.

A

Plasma

75
Q

The ______ zone surrounds a GC and contains tightly packed small B cells of the primary follicles, pushed aside by GCs.

A

Mantle

76
Q

Ag- induced cross-linking of the BCRs and signaling induces several cellular responses including –

1) Production of proteins that promote survival and proliferation, expression costimulators and cytokine receptors that promote interactions with and responsiveness to helper T cells.
2) The expression of ______ induces migration of the cells toward the T cell zone.

A

CCR7

77
Q

A _______ is an activated B cell that is enlarged and proliferating in the GC of a secondary lymphoid follicle.

A

Centroblast

78
Q

The most distinctive cell types in the marginal zone are…

A

Marginal-zone (MZ) macrophages

Marginal B cells

79
Q

Lymphocytes and DCs can enter the _____ _____ from the marginal sinus by passing through a layer of sinus-lining cells that form a barrier between the marginal zone and the _____ _____.

A

White pulp

White pulp

80
Q

A framework of reticular _______ forms the basis of the marginal zone.

A

Fibroblasts

81
Q

Splenic MZ ______ serve as sentinels at the interface between the circulation and lymphoid tissue.

A

B cells

82
Q

MZ B cells rapidly respond to blood-borne viruses and encapsulated bacteria by adopting “________” defensive strategies that blur the conventional boundaries of innate and adaptive immunity.

A

Crossover

83
Q

MZ B cells mount rapid Ab responses to both T cell-dependent and T cell-independent _____.

A

Ags

84
Q

MZ B cells may produce _____ and class-switched ____ and ____ Abs in response to commensal Ags that physiologically translocate from the intestinal mucosa to the general circulation in the absence of infection.

A

IgM
IgG
IgA

85
Q

This innate-like humoral response of MZ B cells may generate a ready-to-use pre-immune antibody repertoire that provides a rapid systemic line of defense not only against pathogens, but also against commensal bacteria that breach the _______ barrier.

A

Mucosal

86
Q

MZ B cells have a lower activation threshold than follicular B cells, which permits the rapid initiation of IgM production and of IgG- and IgA-inducing class-switch recombination (CSR) in the absence of CD40-dependent help from _______ cells.

A

T-FH

87
Q

This T cell-independent pathway requires dual BCR and TLR engagement by conserved microbial Ags together with co-stimulatory signals from DCs and macrophages via various ________.

A

Cytokines

88
Q

The Ags presented to MZ B cells are generally in native conformation which are not processed ______.

A

APCs

89
Q

Ags in immune complexes may bind to _____ complement receptors on MZ B cells. MZ B cells can transfer the immune complex-containing Ags to follicular DCs.

A

CR2

90
Q

Blood-borne pathogens may be captured by __________ DCs in the blood and transported to the spleen, where they may be delivered to MZ B cells.

A

Plasmacytoid (pDCs)

91
Q

In the spleen, polysaccharide Ags can be captured by MZ ________ and displayed or transferred to MZ B cells in this area.

A

Macrophages

92
Q

After entering the splenic MZ via the marginal sinus, TI Ags are captured by MZ _________. Alternatively, TI antigens are captured by ______ and ______ in the circulation.

A

Macrophages
DCs
Neutrophils

93
Q

Ag-presenting MZ macrohages stimulates MZ B cells via the ______ and ______. The stimulation delivers signals that induce class-switch recombination and Ab production after ligating ______ and a proliferation-inducing ligand (______), which are released by APCs in response to microbial TLR ligands.

A

BCR
TLRs
BAFF
APRIL

94
Q

APCs, including red pulp DCs and macrophages, also secrete _____, ______, and type I _______ (IFNs). These cytokines cooperate with BAFF and APRIL to promote the differentiation and survival of IgM-secreting or class-switched IgG-secreting plasma cells.

A

IL-6
IL-10
Interferons

Immunology (10 decks)

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