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BMS 212 > Chapter 17: Adaptive Specific Host Defenses Slides > Flashcards

Chapter 17: Adaptive Specific Host Defenses Slides Flashcards

1
Q

What are the agranulocytic lymphocytes of the adaptive immune system?

A

T cells
B cells
Natural Killer cells (NK)

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2
Q

What are the two types of adaptive immune responses?

A

Cell-mediated immune response
Antibody immune responses which includes the humoral immune response.

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3
Q

What is an antigen?

A

A molecule that is recognized by a specific antibody or the T-cell receptor (TCR) on a T cell.

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4
Q

What macromolecule is usually an antigen?

A

Protein.

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5
Q

What is an epitope?

A

A discrete part of antigen that antibody/TCR recognizes.

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6
Q

Which are mores specific PAMPs or antigens?

A

Antigens.

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7
Q

What are exogenous antigens?

A

Include toxins and other components of microbial cell walls, membranes, flagella, and pilli.

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8
Q

What are endogenous antigens?

A

Produced by microbes that reproduce inside a body’s cells.

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9
Q

What are auto-antigens?

A

Usually a normal protein or complex of proteins that is recognized by the immune system of patients suffering from a specific autoimmune disease. Derived from normal cellular processes.

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10
Q

How can T cells recognize an antigen?

A

T cells can only recognize antigen through Major Histocompatibility Complex (MHC).

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11
Q

What are the two classes of MHC?

A

MHC I and MHC II.
They have different roles and are found on different cells.

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12
Q

What are CD 4 + T cells?

A

Helper T cells.

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13
Q

What antigen complex do CD 4+ T cells recognize?

A

MHC II

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14
Q

What antigen complex do CD 8+ T cells recognize?

A

MHC I

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15
Q

What are CD 8+ T cells?

A

Cytotoxic T cells.

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16
Q

Where are MHC II receptors found?

A

They are found on immune cells; specifically macrophages, dendritic cells, and B cells.

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17
Q

What is the MHC II antigen derived from?

A

Derived from previously phagocytized material (bacteria, viruses, proteins).

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18
Q

What is the role of helper T cells?

A

To coordinate the immune response by the secretion of different cytokines.

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19
Q

What is the primary role of cytotoxic T cells?

A

They remove intracellular pathogens by inducing apoptosis.

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20
Q

What are the two pathways that cytotoxic cells use to induce apoptosis?

A

Perforin-granzyme pathway and CD95 pathway.

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21
Q

What is synthesized during the perforin-granzyme pathway?

A

Involves the synthesis of special killing proteins.

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22
Q

How does the perforin-granzyme pathway work?

A

Perforin punches a hole in the membrane and creates a complex (pore in the membrane).
Granzymes activate apoptotic enzymes that induce apoptosis.

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23
Q

How does the CD95 pathway work?

A

CD95L (T cells) makes a bridge with CD965 to the virally infected cell.
Enzymatic portion of CD95 becomes active, which activates enzymes to induce apoptosis.

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24
Q

What cells are MHC I made by?

A

All cells except RBCs because they do not have a nucleus.

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25
Q

What is the first step of CD4+ T cell activation?

A

TCR binds to MHC-II with recognized antigen and the T cell becomes primed.

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26
Q

What is the second step of CD4+ T cell activation?

A

The second co-stimulation signal occurs with additional APC and TCR signaling complexes.

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27
Q

True or False: MHC-1 and CD8+ T cells allow for detection and clearance of infected walls.

A

True

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28
Q

What is MHC-I antigen derived from?

A

The cytoplasm of infected cells.

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29
Q

What things are being loaded into the MHC-I antigen?

A

Antigen from proteins being degraded and recycled from the cytoplasm.

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30
Q

True or False: MHC-I antigen can be derived from intercellular pathogens but not host-derived.

A

False; it can be both.

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31
Q

What is the first step of CD8+ T cell activation?

A

1st signal occurs upon TCR binding to MHC-I with recognized antigen and causes an increase in IL-2 receptors.

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32
Q

What is the second step of CD8+ T cell activation?

A

Second signal occurs when a CD4+ T cell is stimulated via MHC-II and secretes IL-2, which binds to IL-2 receptors on CD8+ T cells.

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33
Q

Where can you find B cells and antibodies in the body?

A

The spleen, lymph nodes, and MALT (Mucosa-associated lymphatic tissue). A small amount circulates in the blood.

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34
Q

What is the major function of B cells?

A

The secretion of antibodies.

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35
Q

True or False: Each B cell generates a single BCR that recognizes only one epitope.

A

True.

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36
Q

What forms the antigen-binding sites of BCRs?

A

Two variable regions.

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37
Q

What are the specific cells antibodies are secreted from?

A

Plasma cells.

38
Q

What are antibodies?

A

Immunoglobulins similar to BCRs.

39
Q

True or False: Plasma cells have antigen-binding sites and antigen specificity identical to the BCR of the activated B cell.

A

True.

40
Q

Where are antibodies found?

A

Serum or mucosal secretions.

41
Q

What are the 5 major antibody categories?

A

IgG, IgA, IgM, IgD, and IgE.

42
Q

What is the IgM antibody?

A

It is pentameric in shape and is first produced in humoral immune response.

43
Q

What is the IgA antibody?

A

It forms dimers, is the primary type found in secretions.

44
Q

What is the IgG antibody?

A

It is monomeric in shape and is the primary type found in blood and extracellular fluid.

45
Q

What is the IgE antibody?

A

It is monomeric in shape and has low levels in blood and extracellular fluid, mainly found in tissue bound by mase cells and participates in allergic reactions.

46
Q

What is complementary to epitopes?

A

Antigen-binding sites.

47
Q

What are the different functions of antibodies?

A

Activation of complement and inflammation
Neutralization
Opsonization
Killing by oxidation
Agglutination
Antibody-dependent cellular cytotoxicity (ADCC)

48
Q

What is neutralization?

A

When antibodies block the toxins of bacteria and viruses so they cannot bind and cannot replicate.

49
Q

What is opsonization?

A

Macrophages can recognize the Fc receptor protein in antibody and makes it want to eat it more.

50
Q

What is oxidation?

A

Converting molecular oxygen into hydrogen peroxide to kill the bacterial cell.

51
Q

What is agglutination?

A

When antibodies connect bacterial cells all together, stopping them from getting into the bloodstream or deeper tissue.

52
Q

What is antibody-dependent cell-mediated cytotoxicity?

A

NK cell binds to Fc receptor protein of antibodies.
Perforin allows granzyme to enter, which triggers apoptosis and lysis.

53
Q

What does the initiation of the complement system do?

A

Promotes the inflammatory response, recruiting phagocytes to site of infection, enhancing phagocytosis by opsonization, and killing gram-negative bacteria pathogens with the membrane attack complex (MAC).

54
Q

What are the two steps of T cell-dependent B cell activation?

A

Binding directing to antigen (phagocytize antigen).
Present antigen via MHC II (second signal comes from helper T cells (CD4+) (TH2)).

55
Q

What is special about the B cells formed from T cell-dependent B cell activation?

A

They are the only B cells that can form memory.

56
Q

What are the two steps of T cell-independent B cell activation?

A

T1-T1 Antigen stimulation with PRR stimulation (at the same time).
T2-T2 Antigen that directly stimulates B cells (Often contains repeating subunits).

57
Q

What are plasma cells?

A

Fully matured B cells.

58
Q

What do plasma cells do?

A

Secrete anitbodies.

59
Q

What happens first after the B cells are activated?

A

They proliferate through clonal expansion which is when B cells clone themselves and differentiate.

60
Q

Where do B cells develop?

A

The bone marrow.

61
Q

Why do BCRs have massive diversity?

A

A complex series of gene-slicing events.

62
Q

True or False: Only 10% of B cells make it out of the bone marrow.

A

True

63
Q

When is a B cell called an immature B cell?

A

After gene rearrangement and expression of unique BCR cell.

64
Q

What happens if the BCR reacts with its antigen during the immature B cell stage?

A

Apoptosis.

65
Q

Why does apoptosis occur if BCR reacts with its antigen?

A

It prevents the release of self-reactive B cells.

65
Q

Why does apoptosis occur if BCR reacts with its antigen?

A

It prevents the release of self-reactive B cells.

66
Q

What type of antibody do all B cells secrete first?

A

IgM.

67
Q

What is isotype switching?

A

A splicing event in B cell DNA which can result in changes to the Fc region but leaves the variable region unchanged.

68
Q

When does isotope switching occur?

A

After B cell activation.

69
Q

What is the new isotype dependent on?

A

Cytokine signals.

70
Q

During isotype switching, which class of antibody do you want lots of?

A

IgG.

71
Q

What is affinity maturation?

A

After activation B cells increase the mutation rate of the genes encoding for the variable region (antigen binding) f the BCR and therefore antibody.

72
Q

What does affinity maturation result in?

A

Some B cells will have higher affinity for an antigen.

73
Q

What does the higher affinity do for B cells within the germinal center (site within lymph nodes/spleen)?

A

It increases the amount of stimulatory signals given to these B cells.

74
Q

Where do the stimulatory signals in the germinal center come from?

A

Dendritic cells presenting antigen.

75
Q

What does the increase of stimulatory signals to B cells in the germinal center do?

A

Increases the rate of growth of these high-affinity cells.

76
Q

What are some characteristics of memory B cells?

A

Long-lived
Easier to induce antibody secretion
Produce IgG
High affinity for antigen
Provides immunity

77
Q

True or False: B cells that have undergone affinity maturation are not more likely to become memory B cells.

A

False.

78
Q

Where do all leukocytes come from?

A

The bone marrow.

79
Q

What cells migrate from bone marrow to the thymus?

A

Prothymocytes (T cell precursors).

80
Q

What do the thymocytes lack upon arrival to the thymus?

A

TCRs, CD4, and CD8.

81
Q

True of False: Quickly upon arriving at thymus the thymocytes express CD4, CD8, and TCRs.

A

True.

82
Q

True or False: Most thymocytes will not survive and 95%-99% will be “weeded out”.

A

True.

83
Q

What is the cortex of the thymus?

A

The dense outer region.

84
Q

What is the medulla of the thymus?

A

The looser inner region.

85
Q

What are the epithelial reticular cells in the thymus?

A

Macrophages, dendritic cells and epithelial cells there to teach the T cells.

86
Q

What is the first round of selection for T cells?

A

Positive selection, where T cells must recognize MHC I or MHC II with or without peptide.

87
Q

What happens if the T cells don’t recognize MHC I or MHC II?

A

They die.

88
Q

What happens to the T cells that interact with MHC I?

A

They quickly stop expressing CD4.

89
Q

What happens to the T cells that interact with MHC II?

A

They quickly stop expressing CD8.

90
Q

What is the second round of T cell selection?

A

Negative selection where T cells interact with antigen-presenting cells which present self-antigen.

91
Q

What happens if a T cell binds to and recognizes self-antigen?

A

They are eliminated.

BMS 212 (24 decks)

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