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USMLE® Step 1 > USMLE (S1) Immunology > Immunology - Lymphocytes > Flashcards

Immunology - Lymphocytes Flashcards

1
Q

This image shows an antigen-presenting cell activating a CD4 Th cell. Identify (A-E), which all activate the Th cell.

A

(A) MHC II; (B) T-cell receptor; (C) CD4; (D) B7; (E) CD28

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2
Q

Shown here are two cells coactivating a third cell critical to cellular immunity. Identify the cells involved (A-C).

A

(A) virus-infected cell; (B) Th cell (CD4); (C) Tc cell (CD8+)

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3
Q

This image shows a Th cell inducing a B cell to class switch and make antibodies. Identify (A-C), which all activate the B cell.

A

(A) Th2 cytokines (interleukin-4, -5, and -6); (B) CD40L; (C) CD40

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4
Q

Identify and describe the process shown, in which the coating of a bacterium with antibodies summons an important immune cell.

A

Opsonization, in which an antibody promotes the phagocytosis of an antigen by a phagocyte

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5
Q

Identify and describe the process shown, in which the coating of a bacterium with antibodies prevents it from approaching the cells.

A

Neutralization, in which an antibody attaches to an antigen and prevents adherence to cells

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6
Q

Which cells are responsible for innate immunity?

A

Neutrophils, macrophages, dendritic cells, natural killer cells, and the complement system

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7
Q

_____ (Adaptive/Innate) immunity is encoded into the germ line and reacts to a set of static parameters that humans have adapted to combat over evolutionary time.

A

Innate

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8
Q

_____ (Adaptive/Innate) immunity has target molecules that are encoded in the germline as opposed to reacting to novel challenges.

A

Innate

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9
Q

What is the benefit of germline encoding of target antigen recognition by the innate immune system?

A

It allows innate immunity to be both fast and nonspecific

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10
Q

How does the adaptive immune response differ during first and second exposures to an antigen?

A

Adaptive immunity is slow to develop on first exposure but fast on any subsequent exposures

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11
Q

What are the components of the adaptive immune system?

A

T cells, B cells, and circulating antibody

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12
Q

Th1 and Th2 cells are specialized descendants of which type of cell?

A

CD4+ helper T cells

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13
Q

What type of T cells activate macrophages and CD8+ T cells by producing interleukin-2 and γ-interferon?

A

Th1 cells

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14
Q

What type of T cells activate B cells to make antibody by producing interleukin-4 and interleukin-5?

A

Th2 cells

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15
Q

What is the effect of interleukin-12 on T cells?

A

It induces the differentiation of naive helper T cells into Th1 cells, resulting in increased cell-mediated immunity

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16
Q

What is the role of interleukin-4 in T-cell maturation?

A

Interleukin-4 induces the differentiation of native helper T cells to Th2 cells resulting in increased antibody-mediated immunity

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17
Q

Th1 cells have what functions?

A

The activation of macrophages and CD8+ T cells by producing interleukin-2 and γ-interferon

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18
Q

Th2 cells have what functions?

A

The activation of B cells to make antibodies by producing interleukin-4 and interleukin-5

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19
Q

Where in the body are T cell precursors found?

A

In the bone marrow

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20
Q

T cell precursor cells give rise to what cell type?

A

CD4+/CD8+ T cells

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21
Q

CD4+/CD8+ T cells are found where?

A

In the cortex of the thymus

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22
Q

CD4+ T cells give rise to what cell line?

A

Helper T cells

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23
Q

CD8+ T cells give rise to what cell line?

A

Cytotoxic T cells

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24
Q

Interleukin-10 inhibits _____ (Th1/Th2) cells.

A

Th1 cells

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25
Q

What is the name of the set of genes that encode the major histocompatibility complex?

A

Human leukocyte antigen genes

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26
Q

On which cells is major histocompatibility complex I expressed?

A

Almost all nucleated cells

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27
Q

What are the three major histocompatibility complex I class genetic loci?

A

Human leukocyte antigen-A, human leukocyte antigen-B, and human leukocyte antigen-C

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28
Q

Which cells express major histocompatibility complex II?

A

Antigen-presenting cells

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29
Q

What are the three major histocompatibility complex II class genetic loci?

A

Human leukocyte antigen-DR, human leukocyte antigen-DP, and Human leukocyte antigen-DQ

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30
Q

For cells expressing major histocompatibility complex I, where is antigen loaded into the peptide-binding groove? Where does this occur for cells expressing major histocompatibility complex II?

A

Antigen is loaded into the rough endoplasmic reticulum of mostly intracellular peptides for cells expressing major histocompatibility complex I; for cells expressing major histocompatibility complex II, antigen is loaded in acidified endosomes

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31
Q

Which major histocompatibility complex mediates viral immunity?

A

Major histocompatibility complex I mediates viral immunity (via interaction with CD8+ T cells)

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32
Q

Which protein is paired with major histocompatibility complex I?

A

β2-microglobulin

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33
Q

On cells that express major histocompatibility complex II, where is antigen loaded into the peptide-binding groove?

A

Antigen is loaded in acidified endosomes

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34
Q

Which human leukocyte antigen subtype is associated with psoriasis, ankylosing spondylitis, inflammatory bowel disease, and Reiter’s syndrome?

A

B27

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35
Q

Which four autoimmune-related conditions are associated with human leukocyte antigen subtype B27?

A

Psoriasis, Ankylosing spondylitis, Inflammatory bowel disease, and Reiter’s syndrome (remember: PAIR

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36
Q

Which human leukocyte antigen subtype is associated with Graves’ disease?

A

B8

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37
Q

Which human leukocyte antigen subtype is associated with multiple sclerosis, hay fever, systemic lupus erythematosus, and Goodpasture’s syndrome?

A

DR2

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38
Q

Which two human leukocyte antigen subtypes are associated with type 1 diabetes mellitus?

A

DR3 and DR4

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39
Q

Which human leukocyte antigen subtype is associated with rheumatoid arthritis?

A

DR4

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40
Q

Which human leukocyte antigen subtype is associated with pernicious anemia and Hashimoto’s thyroiditis?

A

DR5

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41
Q

Which human leukocyte antigen subtype is associated with steroid-responsive nephrotic syndrome?

A

DR7

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42
Q

Which human leukocyte antigen subtype is associated with hemochromatosis?

A

A3

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43
Q

What is the primary function of B cells?

A

To make antibodies

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44
Q

Which types of organ graft rejections are mediated by B cells? By T cells?

A

B cells mediate hyperacute organ graft rejection; T cells mediate acute and chronic organ graft rejection

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45
Q

Do immunoglobulin G antibodies bind to bacteria, viruses, or both?

A

Both; immunoglobulin G opsonizes bacteria and inactivates viruses by binding them

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46
Q

Which immunoglobulin mediates allergic reactions (type I hypersensitivity)?

A

Immunoglobulin E

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47
Q

Which hypersensitivity reactions are mediated by immunoglobulin G?

A

Type II and type III hypersensitivity reactions

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48
Q

What are the primary functions of CD4+ T cells?

A

To induce B cells to make antibodies; to produce γ-interferon to activate macrophages

49
Q

Which T cells are cytotoxic to cells infected by viruses?

A

CD8+ cells

50
Q

Which immune cells mediate type IV hypersensitivity reactions?

A

T cells

51
Q

Which three cytokines enhance activity of natural killer cells?

A
  • Interleukin-2 (IL-2)
  • Interleukin-12 (IL-12)
  • Interferon-γ (IFN-γ)
52
Q

Which two signals induce natural killer cell killing activity?

A
  • Exposure to the activation signal on infected target cells.
  • Absence of major histocompatibility complex I on the target cell surface.
53
Q

Natural killer cells exhibit killing activity against which two types of cells?

A

Virally infected cells and tumor cells

54
Q

Natural killer cells use _____ and _____ to induce apoptosis in target cells.

A

Perforins and granzymes

55
Q

Helper T cells have CD4, which helps them bind to major histocompatibility complex ___ (I/II) on antigen-presenting cells.

A

Major histocompatibility complex II

56
Q

Cytotoxic T cells have CD 8, which binds to major histocompatibility complex ___ (I/II) on virus-infected cells.

A

Major histocompatibility complex I

57
Q

CD4 cells recognize major histocompatibility complex _____ (I/II), while CD8 cells recognize major histocompatibility complex _____ (I/II).

A

II; I

58
Q

What is the CD3 complex?

A

A cluster of polypeptides involved in T-cell signal transduction

59
Q

Name three antigen-presenting cells.

A

Macrophage, B cell, and dendritic cell

60
Q

When macrophages and lymphocytes interact, each releases cytokines that stimulate the other. What are the cytokines?

A

Lymphocytes release interferon-γ and macrophages release interleukin-1 and tumor necrosis factor-

61
Q

Which two species of gram positive bacteria produce superantigens?

A

Streptococcus pyogenes and Staphylococcus aureus

62
Q

Bacterial superantigens cross-link _____ to _____.

A

T-cell receptors; major histocompatibility complex II

63
Q

Which immune cells are involved in the body’s response to endotoxins on gram negative organisms?

A

Endotoxin directly stimulates macrophages

64
Q

Which three cytokines are released as a result of superantigen-caused activation of macrophages?

A

Interleukin-1, interleukin-6, tumor necrosis factor-

65
Q

Which subtype of helper T cell is activated by superantigens?

A

Th1 cells (which subsequently cause cytokine release from macrophages)

66
Q

Which receptor does endotoxin bind to on macrophages?

A

CD14

67
Q

Superantigen binding results in uncontrolled release of _____ from T cells.

A

Interferon-γ

68
Q

In immune reactions, the presence of a costimulatory signal via B7 and CD28 interaction is important in the activation of what type of cell?

A

T cells

69
Q

What is the first step in the activation of helper T cells by antigen-presenting cells?

A

Antigen-presenting cells present a phagocytosed foreign body to the helper T cell

70
Q

Which molecule on the antigen-presenting cell surface presents foreign antigens to helper T cells?

A

Major histocompatibility complex II

71
Q

During T-cell activation, what part of the helper T cell recognizes the foreign antigen?

A

The T-cell receptor recognizes antigens bound to major histocompatibility complex II of antigen-presenting cells

72
Q

What is the origin of the proteins presented with major histocompatibility complex I molecules to cytotoxic T cells?

A

Proteins are endogenously synthesized and presented on major histocompatibility complex I

73
Q

What part of the cytotoxic T cell recognizes the proteins that are presented on major histocompatibility complex I?

A

The T-cell receptor

74
Q

In addition to the interaction of the major histocompatibility complex II and the T-cell receptor, what other interaction is required for T-cell activation?

A

The interaction of B7 and CD28 (this is signal 2 of T-cell activation)

75
Q

What is the function of an activated helper T cell?

A

Synthesis and secretion of cytokines

76
Q

What cytokine from helper T cells activates cytotoxic T cells to kill virus-infected cells?

A

Interleukin-2, which is the second signal required after the interaction of major histocompatibility complex I and T-cell receptors

77
Q

Which type of helper T cell produces the cytokines that serve as a signal for B-cell class switching?

A

Th2 cells

78
Q

Which three cytokines may serve as a signal in B-cell class switching?

A

Interleukin-4, interleukin-5, interleukin-6

79
Q

In addition to cytokines released by helper T cells, what other signal is required for B-cell activation?

A

CD40 receptor binding to CD40 ligand on helper T cell

80
Q

Which parts of the antibody light and heavy chains recognize antigen?

A

The variable sections

81
Q

Which two antibody types fix complement?

A

Immunoglobulin M and Immunoglobulin G

82
Q

What are the 4 C’s that are important to remember about the Fc fragment of an antibody?

A

Constant region, Carboxy terminal, Complement binding, and Carbohydrate side chains

83
Q

Name four different mechanisms by which antibody diversity is generated.

A

The random recombination of VJ (light-chain) or VDJ (heavy-chain) genes, the random combination of heavy and light chains, somatic hypermutation, and the addition of nucleotides to DNA during genetic recombination by terminal deoxynucleotidyl transferase

84
Q

What is the process called whereby an antibody promotes the phagocytosis of an antigen by a phagocyte?

A

Opsonization

85
Q

What is the process called whereby an antibody attaches to an antigen and prevents adherence to cells?

A

Neutralization

86
Q

Antibodies triggering the sequence that leads to the activation of the membrane attack complex have activated what part of the immune system?

A

Complement

87
Q

When an antibody activates complement which two bacteria-killing processes are enhanced?

A

Opsonization and lysis

88
Q

What part of the antibody binds complement?

A

The Fc fragment

89
Q

What stimulus causes somatic hypermutation to generate antibody diversity?

A

Antigen stimulation

90
Q

Which two immunoglobulin isotypes do mature B cells express on their surfaces?

A

Immunoglobulin M and immunoglobulin D

91
Q

B cells can be induced to become which type of antibody-secreting cell?

A

Plasma B cells

92
Q

Which signals mediate antibody class switching?

A

Cytokines and CD40 ligand

93
Q

Which three classes of immunoglobulins do plasma cells secrete?

A

Immunoglobulin A, immunoglobulin E, and immunoglobulin G

94
Q

Which immunoglobulin is the main antibody that is involved in the secondary response?

A

Immunoglobulin G

95
Q

Which immunoglobulin is most abundant?

A

Immunoglobulin G

96
Q

Which immunoglobulin fixes complement, crosses the placenta, opsonizes bacteria, and neutralizes bacteria toxins and viruses?

A

Immunoglobulin G

97
Q

Which immunoglobulin prevents the attachment of bacteria and viruses to mucous membranes but cannot fix complement?

A

Immunoglobulin A

98
Q

Which immunoglobulin is found in secretions?

A

Immunoglobulin A

99
Q

How does the structure of immunoglobulin A differ in secretions vs plasma?

A

Immunoglobulin A can be either a monomer or a dimer

100
Q

Which immunoglobulin is produced as part of the primary response to an antigen, fixes complement, but does not cross the placenta?

A

Immunoglobulin M

101
Q

Which immunoglobulin is the antigen receptor on the surface of B cells?

A

Immunoglobulin M

102
Q

Which immunoglobulin can be monomer or pentamer?

A

Immunoglobulin M

103
Q

Which immunoglobulin has an unclear function and can be found on the surface of B cells and in serum?

A

Immunoglobulin D

104
Q

Which immunoglobulin mediates immediate (type I) hypersensitivity by inducing the release of mediators from mast cells and basophils when an individual is exposed to an allergen?

A

Immunoglobulin E

105
Q

Which immunoglobulin mediates immunity to helminths and has the lowest concentration in serum?

A

Immunoglobulin E

106
Q

Which type of antibody activates eosinophils?

A

Immunoglobulin E

107
Q

Immunoglobulin G molecules from two individuals represent two different _____ of the same class of immunoglobulins because they are encoded by two different alleles of the same gene.

A

Allotypes

108
Q

Define antibody allotype and isotype.

A

Allotypes are genetic polymorphisms within the population; isotypes are the five heavy chains of antibodies

109
Q

Are isotypes (immunoglobulin A, immunoglobulin E, etc) determined by the light chain or heavy chain?

A

Heavy chain

110
Q

Two antibodies of the same allotype and isotype that bind different antigens are different _____.

A

Idiotypes

111
Q

What region of the antibody accounts for the unique antigen binding site, which ultimately distinguishes between idiotypes?

A

Hypervariable region

112
Q

How do the molecular structures of thymus-dependent and -independent antigens differ?

A

Thymus-dependent antigens lack the peptide component

113
Q

Thymus-independent antigens stimulate release of which type of antibodies?

A

Immunoglobulin M only

114
Q

How does the immune response to thymus-dependent and -independent molecules differ?

A

Only thymus-dependent antigens generate immunologic memory

115
Q

An antigen lacking a peptide component cannot undergo which process that promotes antibody class switching and immunologic memory?

A

Thymus independent lack a peptide component, cannot be presented to T cells, do not promote isotype switching, and do not result in immunologic memory

116
Q

Why is a peptide component added to the Haemophilus influenzae antigen used as a vaccine?

A

In vaccine form, Haemophilus influenzae is conjugated to protein, which makes it thymus dependent

117
Q

This is an MHC class ____ (I/II) molecule, made of ____ and ____ chains, and expressed in ____ cells. It does not bind ____ (CD4/CD8/TCR).

A

MHC class II; α and β chains; antigen-presenting cells; CD8

118
Q

This is an MHC class ____ (I/II) molecule, made of a(n) ____ chain paired with a(n) ____, and expressed in all cells except ____.

A

MHC class I; α chain; β2-microglobulin; red blood cells

USMLE (S1) Immunology (4 decks)

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