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Immunology > Leukocyte Circulation And Migration Into Tissue > Flashcards

Leukocyte Circulation And Migration Into Tissue Flashcards

1
Q

In the lymph nodes, Ag-activated B cells seek help of what type of cells?

A

T helper cells.

B cells present antigens to T helper cells. This is important for antibody responses to protein antigens.

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2
Q

What do Ag-activated B cells mature into?

A

Memory cells or plasma cells.

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3
Q

What are plasma cells?

A

Terminally differentiated B cells which produce and secrete larg abouts of Abs.

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4
Q

In the spleen, Ag-activated B cells primarily produce Abs against what type of microbe?

A

Microbial polysaccharides.

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5
Q

What type of cells are found in the periarteolar lymphoid sheath of the spleen?

A

T cells

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6
Q

What type of cells are found in lymphoid follicles?

A

B cells.

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7
Q

In search of forein Ags, where do naive T cells migrate into?

A

Secondary lymphoid organs, such as lymph nodes.

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8
Q

If a T cell is activated by Ags, what does it differentiate into?

A

Effector or memory T cells.

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9
Q

Where do effector and memory T cell migrate back into?

A

Peripheral sites of infection.

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10
Q

Where do some activated and differentiated T cells do?

A

The remain in the LNs and help Ag-activated B cells to become an “Ab factory”

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11
Q

Once effector B cells secrete Abs, where do the Abs go?

A

They enter the blood and are delivered to sites of infection.

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12
Q

In the absence of Ag stimulation, what type of follicles are found in the LN?

A

Primary follices.

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13
Q

When is a primary follicle converted into a secondary follicle?

A

With Ag stimulation. This converts the primary follicle into a secondary follicle or germinal center.

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14
Q

The activation of T cells requires what type of cells?

A

Professional Ag-presenting cells.

These include:

DCs

Tissue macrophages

B cells.

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15
Q

What are antigen-presenting cells (APCs)?

A

Cells that capture and process Ags to lymphocytes and provide signals that stimulate the proliferation and differentiation of the lymphocytes.

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16
Q

What cells display Ag to T cells? Are they required for B cells?

A

APC. They are not required for B cells.

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17
Q

What are the only cells capable of activating naive T cells in the LNs?

A

Dendritic cells

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18
Q

Naive B cells migrate into what type of lymphoid tissues?

A

Secondary lymphoid tissues.

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19
Q

DCs and macrophages are cells of innate immunity. What is also of significance of the two?

A

They provide a link between innate and adaptive immunity.

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20
Q

What is the primary role of dendritic cells?

A

They activate naive T cells.

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21
Q

How do DCs acquire Ags?

A

They use phagocytosis, receptor-mediated endocytosis and pinocytosis.

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22
Q

What do activated DCs secrete?

A

Cytokines

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23
Q

Where do classical DCs reside?

A

Skin

Mucosa

Organ parenchyma

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24
Q

When classical DCs are activated, where do they migrate to?

A

LNs where they display microbial protein Ags to T lymphocytes.

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25
Q

Plasmacytoid DCs are early responders to what type of infections?

A

Viral infections.

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26
Q

During inflammatory responses in tissues, dendritic cells may also be derived from what molecule?

A

Monocytes

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27
Q

FDCs reside in the lymphoid follices of what organs?

A

Lymph nodes

Spleen

Mucosal lymphoid tissues

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28
Q

FDCs bind and display Ags on their surfaces for recognition by what molecules?

A

B lymphocytes

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29
Q

What is migration/recruitment?

A

The general process of leukocyte movement from blood into tissues.

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30
Q

What is recirculation?

A

The ability of lymphocytes to repeatedly:

Home to secondary lymphoid organs

Reside there transiently

Return to the blood.

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31
Q

What is leukocyte homing?

A

Cell migration out of the blood and into peripheral tissues, or to a site of an infection or injury.

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32
Q

The recruitment of leukocytes and plasma proteins from the blood to sites of infection and tissue injury is a major part of what process?

A

Inflammation.

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33
Q

What is inflammation triggered by?

A

Recognition of microbes and dead tissues in innate immunen responses.

Inflammation is refined and prolonged during adaptive immune responses.

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34
Q

What is the funciton of an inflammatory response?

A

It delivers the cells and molecules of host defense to the sites where offending agents need to be combated.

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35
Q

Circulating leukocytes move hrough what mechanisms?

A

Tethering

Rolling

Adhesion and stop

Transmigration in the tissue.

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36
Q

How does tethering occur?

A

Through transient interactions of selectins and integrin with their ligands.

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37
Q

What is the purpose of leukocytes rolling?

A

It allows chemokine receptors on leukocytes to bind chemokines expressed on endothelium.

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38
Q

How do leukocytes adhere to the endothelium?

A

Receptors signal and activate integrins on leukocytes which interact with ligands expresssed on the endothelium.

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39
Q

As leukocytes migrate, they follow a gradient established by what molecule?

A

Chemokines

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40
Q

Are adhesion molecules found on healthy or unhealthy endothelial cells?

A

Unhealthy

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41
Q

Would you expect endothelial cells at sites of injection and tissue injury to express adhesion molecules?

A

Yes

42
Q

Leukocyte/lymphocyte homing and recruitemnt require the temporary adhesion of the leukocyte to the endothelial cells of blood vessels.

A

:)

43
Q

What are addressins?

A

A set of several adhesion molecules on the surface of endothelial cells.

44
Q

What type of selectin is found on endothelium activated by histamine or thrombin?

A

P-selectin

45
Q

What type of selectin is found on the endothelium activated by cytokines?

A

E-selectin

46
Q

What type of selectin is associated with neutrophils, monocytes, T cells and B cells?

A

L-selectin

47
Q

Which selectins are found on endothelial cells?

A

P selectin and E selectin.

48
Q

Where is L-selectin expressed only?

A

On leukocytes and lymphocytes

49
Q

What is L-selectin activated by?

A

IL-1 and TNF.

50
Q

What is L-selectin important for?

A

Naive T and B lymphocytes for homing into LNs by interacting with high endothelial venules.

51
Q

What is the function of an integrin?

A

It integrates signals triggered by extracellular ligans with cytoskeleton-dependent motility, shape change and phaogcytic responses.

52
Q

What is a function of an integrin?

A

It mediates adhesion of cells to other cells or to extracellular matrix via various specific ligands.

53
Q

What is a function of integrins?

A

They mediate adhesion of cells to other cells or to extracellular matrix via various specific ligans.

54
Q

What is integrin activation?

A

Integrin activaiton is when integrins are able to respond to intracellular signals by rapidly increasing their affinity.

55
Q

Integrin activation occurs in all leukocytes in response to what?

A

Chemokine binding to chemokine receptors.

56
Q

When does integrin activation occur in T lymphocytes?

A

When Ag binds to TCRs

57
Q

What is integrin activation mediated by?

A

Chemokine-induced conformational changes in the extracellular domains of integrins. It leads to an increased affinity for integrins.

58
Q

Are integrins normall in a low-affinity or high affinity state?

A

Low-affinity.

Activation of leukocyte integrins occurs when rolling of leukocytes occurs.

59
Q

What is a function of chemokines?

A

They stimulate leukocyte movement and regulate the migration of leukocytes from the blood to tissues.

60
Q

Do neutrophils and monocytes require activation to be recruited into tissue sites of infectiono r injury?

A

No

61
Q

How do neutrophils and monocytes enter the tissue?

A

Through post-capillary venules except parencymal tissues (liver, lungs, kidney).

62
Q

What are the functions of myeloid leukocytes?

A

They eliminate infectious pathogens, clear dead tissues and repair the damage.

63
Q

What process occurs during the interaction between P-selectin and ligands on leukocytes?

A

Rolling

64
Q

How do naive T cells enter lymph nodes?

A

Via high endothelial venules

65
Q

How do dendritic cells bearing Ag enter the lymph nodes?

A

Through lymphatic vessels.

66
Q

How do effector and memory T cells get to sites of inflammation?

A

They leave the blood and enter peripheral tissues through venules.

67
Q

T and B lymphocytes both express which selectin?

A

L-selectin.

68
Q

How do naive lymphocytes enter the LN?

A

Through high endothelial venules

69
Q

What is the term for L-selectin ligands expressied on HEV?

A

Peripheral node addressins

70
Q

How do B and T cells migrate to different zones of the LN?

A

By chemokines

71
Q

Ag-loaded DCs enter the LN through … ?

A

Lymphatic vessels

72
Q

HEV is present in what ytpe of lymphoid organ?

A

Secondary lymphoid organs.

73
Q

Naive T lymphocytes home to lymph nodes as a result of…?

A

L-selectin binding to peripheral lymph node addressin on HEV.

74
Q

Naive T cells that have recently entered a LN cannot sense _____ between the T cell zone of the node and the lymph.

A

S1P concentration.

75
Q

Ag-activated T cells have low levels of ____ and the cells stay in the LN.

A

S1PR1

76
Q

Where do activated effector T cells home to?

A

Sites of infection in peripheral tissues.

77
Q

Cell migration into tissue is mediated by what selectins?

A

E and P selectins, as well as integrins and chemokines that are produced at sites of infection.

78
Q

Chemokines and chemokine receptors are involved in what?

A

Effector/memory T cell migration.

79
Q

What is the significance of CD44?

A

It is important for the mobilization of effector T cells in sites of infection and inflammation.

80
Q

At sites of infection, what is secreted by endothelial cells?

A

Chemokines.

E and P seletin is expressed here, as well as hyaluronic acid.

81
Q

CD44 can mediate why type of interactions?

A

Rolling interactions with vascular endothelial cells that express HA

82
Q

Chemokine signaling via GPCRs results in what?

A

Increased integrin affinity.

83
Q

How do naive B cells home to secondary lymphoid tissues throughout the body?

A

They use the same basic mechaisms as do naive T cells.

84
Q

As B cells mature, what chemokine receptor do they express?

A

CXCR5

85
Q

Once B cells express chemokine receptor CXCR5, where do they move?

A

Into the white pulp.

86
Q

Once maturation of B cells is completed in the white pulp, where do mature naive B cells go?

A

They reenter the circulation and home to lymph nodes and mucosal lymphoid tissues.

87
Q

Homing of mature naive B cells from the blood into LNs involves …?

A

Rolling interactions of HEVs, chemokine activation of integrins, and stable arrest.

88
Q

What chemokiens are required for the homing process?

A

CXCL12 and CCL12/CCL21 on HEV and chemokine receptors CXCR4 and CCR7 on naive B cells.

89
Q

In the stroma, B cells migrate into follices drived by ___ recognized by CXCR5 expressed on naive B cells.

A

CXCL13

90
Q

In the follicles, what may B cells encounter that may lead to their activation?

A

Ag

91
Q

What is the function of CCL2?

A

It recruits leukocytes (monocytes).

92
Q

What is the function of chemokine CCL19?

A

T cell and dendritic cell migration into parafollicular zones of lymph nodes.

93
Q

What is the function of CCL21?

A

T cell and dendritic cell migration into parafollicular zones of lymph nodes.

94
Q

What is the major function of chemokines CXCL8?

A

Neutrophil recruitment.

It is also know as IL-8

95
Q

What is the major function of CXCL10?

A

Effector T cell recruitment

It is also known as IP-10

96
Q

What is the function of chemokine CXCL-13?

A

B cell migration into follicles

T folllicular helper cell migration into follicles.

97
Q

What is the function of chemokine CXCL12?

A

Homing naive B cells to lymph nodes.

Its original name is SDF-1 alpha beta

98
Q

What chemokines are used during activation of luekocytes?

A

IL-8, MCP-1

99
Q

What molecules are used during capture and rolling phases of leukocytes?

A

E-selectin

100
Q

What adhesion molecules are used to adhere leukocytes to endothelial cells?

A

VCAM-1, ICAM-1

101
Q

During transmigration of leukocytes, endothelial cells present what ligand that is recognized by receptors on neutrophils?

A

CXCL8 (also known as IL-8)

Immunology (17 decks)

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