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Immunology > Lymphocytes > Flashcards

Lymphocytes Flashcards

1
Q

What is Innate immunity?

A

Receptors that recognize pathogens are germline encoded

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2
Q

What is the reponse like in Innate immunity?

A

Reponse to pathogens is fast & nonspecific

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3
Q

Is there memory in Innate immunity?

A

No memory

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4
Q

What does Innate immunity consist of?

A
  • Neutrophils
  • Macrophages
  • Dendrictic cells
  • Natural killer cells (lymphoid origin)
  • Complement
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5
Q

What is Adaptive immunity?

A

Receptors that recognize pathogens V(D)J recombination during lymphocyte development

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6
Q

What is the response like in Adaptive immunity?

A

Response is slow on first exposure, but memory response is faster & more robust

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7
Q

What does Adaptive immunity consist of?

A
  • T cells
  • B cells
  • Circulating Ab
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8
Q

What is MHC?

A

Major histocompatibility complex

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9
Q

What is MHC encoded by?

A

Human leukocyte Ag (HLA) genes

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10
Q

What does MHC do?

A

Present Ag fragments to T cells & bind TCR

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11
Q

What are the HLA genes of MHC I?

A

HLA-A, HLA-B, HLA-C

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12
Q

What does MHC I bind to?

A

TCR & CD8

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13
Q

Where is MHC I expressed?

A

On all nucleated cells

Not expressed on RBC

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14
Q

Where are MHC I Ag’s loaded?

A

RER w/ mostly intracellular peptides

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15
Q

What does MHC I mediate?

A

Viral immunity

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16
Q

What does MHC I pair w/?

A

ß2-microglobulin (aids in transport to cell surface)

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17
Q

What are the HLA genes of MHC II?

A

HLA-DR, HLA-DP, HLA-DQ

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18
Q

What does MHC II bind to?

A

TCR & CD4

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19
Q

Where is MHC II expressed?

A

Only on Ag-presenting cells (APCs)

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20
Q

When are the MHC II Ag’s loaded?

A

Following release of invariant chain in an acidified endosome

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21
Q

What dz is HLA-A3 assoc w/?

A

Hemochromatosis

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22
Q

What dz is HLA-B27 assoc w/?

A
  • Psoriasis
  • Ankylosing spondylitis
  • Inflammatory bowel dz
  • Reiter’s synd
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23
Q

What dz are HLA-DQ2/DQ8 assoc w/?

A

Celiac dz

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24
Q

What dz is HLA-DR2 assoc w/?

A
  • Multiple sclerosis
  • Hay fever
  • SLE
  • Goodpasture’s
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25
Q

What dz is HLA-DR3 assoc w/?

A

DM I & Grave’s dz

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26
Q

What dz is HLA-DR4 assoc w/?

A

Rheumatoid arthritis & DM I

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27
Q

What dz is HLA-DR5 assoc w/?

A

Pernicious anemia→ B12 def

Hashiomoto’s thyroiditis

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28
Q

What do Natural Killer cells do?

A

Use Perforin & granzymes to induce apoptosis of virally infected cells & tumor cells

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29
Q

NK cells are the only lymphocyte member of the ____ ____ ____.

A

Innate immune system

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30
Q

What is NK cell activity enhanced by?

A
  • IL-2
  • IL-12
  • IFN-ß
  • IFN-alpha
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31
Q

When are NK cells induced?

A

To kill when exposed to a nonsepcific activation signal on target cell &/or to an absence of class I MHC on target cell surface

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32
Q

What are the B cell functions?

A

Make Ab

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33
Q

What does Ab do?

A
  • Opsonize bacteria
  • Neutralize viruses (IgG)
  • Activate complement (IgG, IgM)
  • Sensitize mast cells (IgE)
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34
Q

What does IgE respond to?

A

Allergy

Type I hypersensitivity

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35
Q

What does IgG respond to?

A

Cytotoxic (type II) & Immune complex (type III) hypersensitivity

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36
Q

What are B cells involved in?

A

Hyperacute & humorally mediated acute & chronic organ rejection

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37
Q

What are the functions of CD4+ T cells?

A

Help B cells make Ab & produce cytokines to activate other cells of immune system

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38
Q

What is the function of CD8+ T cells?

A

Kill virus-infected cells directly

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39
Q

What are T cells involved in?

A

Delayed cell-med hypersensitivity (type IV)

Acute & chronic cellular organ rejection

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40
Q

Where does Positive selection happen?

A

Thymic cortex

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41
Q

What is Positive selection?

A

T cells expressing TCRs capable of binding surface self MHC molecules survive

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42
Q

Where does Negative selection happen?

A

Thymic medulla

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43
Q

What is Negative selection?

A

T cells expressing TCRs w/ high affinity for self Ag’s undergo apoptosis

44
Q

What causes T & B cell activation?

A

Antigen-presenting cells (APCs)

45
Q

What are the APCs?

A
  • Dendrite cell
  • Macrophage
  • B cell
46
Q

What is the only APC that can activate naive T cell?

A

Dendrite cell

47
Q

How many signals are required for T & B cell activation& B cell class switching?

A

Two signals

48
Q

What is the 1st step of Naive T cell activation?

A

Foreign body is phagocytosed by dendritic cell

49
Q

What is the 2nd step of naive T cell activation?

A

Foreign Ag is presented on MHC II & recognized by TCR on Th cell. Ag is presented on MHC to Tc (cytotoxic) cells (signal 1)

50
Q

What is the 3rd step in naive T cell activation?

A

“Costimulatory signal” is given by interaction of B7 & CD28 (signal 2)

51
Q

What is the 4th step in naive T cell activation?

A

Th cell activates & produces cytokines. Tc cell activates & is able to recognize & kill virus-infected cell

52
Q

What is the 1st step of B cell activation & class switching?

A

Helper T cell activation same as naive T cell activation

53
Q

What is the 2nd step of B cell activation & class switching?

A

B cell receptor-med endocytosis; foreign Ag is presented on MHC II & recognized by TCR on Th cell (signal 1)

54
Q

What is the 3rd step of B cell activation & class switching?

A

CD40 receptor on B cell binds CD40 ligand on Th cell (signal 2)

55
Q

What is the 4th step of B cell activation & class switching?

A

Th cell secretes cytokines that determine Ig class switching of B cell. B cell activates & undergoes class switching, affinity maturation & Ab production

56
Q

What do Th1 cells secrete?

A

IFN-gamma

57
Q

What do Th2 cells activate?

A

Macrophages

58
Q

What are Th1 cells inhibited by?

A

IL-4 & IL-10 (from Th2 cell)

59
Q

What do Th2 cells secrete?

A

IL-4, IL-5, IL-10, IL-13

60
Q

What do Th2 cells recruit?

A

Eosinophils for parasite defense & promotes IgE production by B cells

61
Q

What are Th2 cells inhibited by?

A

IFN-gamma (from Th1 cell)

62
Q

What is Macrophage-lymphocyte interaction?

A

Activated lymphocytes (release INF-gamma) & macrophages (release IL-1, TNF-alpha) stim one another

63
Q

Helper T cells have ____ which binds to ____ on ___

A

CD4, MHCII, APCs

64
Q

What do Cytotoxic T cells do?

A

Kill virus-infected, neoplastic & donor graft cells by inducing apoptosis

65
Q

What do Cytotoxic T cells release?

A

Cytotoxic granules containing performed proteins

66
Q

What is perforin?

A

Helps to deliver the content of granules into target cell

67
Q

What is granzyme?

A

A serine protease, activates apoptosis inside target cell

68
Q

What is granulysin?

A

Antimicrobial, induces apoptosis

69
Q

What does CD8 on cytotoxic T cells bind to?

A

MHC I on virus-infected cells

70
Q

What do Regulatory T cells do?

A

Help maintain specific immune tolerance by suppressing CD4 & CD8 T-cell effector functions

71
Q

What do regulatory T cells express?

A

CD3, CD4, CD25 (alpha chain of IL-2 receptor) cell surface makers

72
Q

What do activated regulatory T cells produce?

A

Anti-inflammatory cytokines like IL-10 & TGF-ß

73
Q

What do the variable part of L & H chains on Ab recognize?

A

Antigens

74
Q

What does the Fc portion of IgM & IgG do?

A

Fixes complement

75
Q

What does the Heavy chain of Ab do?

A

Contributes to Fc & Fab fractions

76
Q

What does the Light chain of Ab do?

A

Contributes only to Fab fraction

77
Q

What is the Fab fraction of an Ab?

A
  • Ag-binding fragment
  • Determines idiotype: unique Ag-binding pocket; only 1 antigenic specificity expressed per B cell
78
Q

What is the Fc fraction of an Ab?

A
  • Constant
  • Carboxy terminal
  • Compliment binding at CH2 (IgG + IgM only)
  • Carbohydrate side chains
  • Determines isotype (IgM, IgD, etc)
79
Q

What is Ab diversity generated by?

A
  • Random “recombination” of VJ (light-chain) of V(D)J (heavy-chain) genes
  • Random combo of heavy chains w/ light chains
  • Somatic hypermutation (following Ag stim)
  • Add of nucleotides to DNA during recombination by terminal deoxynucelotidyl transferase
80
Q

What do mature B lymphocytes express?

A

IgM & IgD on their surfaces

81
Q

How can mature B lymphocytes differentiate?

A

Isotype switching into plasma cells that secrete IgA, IgE or IgG

82
Q

What is isotype switching?

A

Gene rearrangement mediate by cytokines & CD40 ligand

83
Q

What is IgG?

A

Main Ab in 2° (delayed) response to an Ag

84
Q

What is the most abundant Ig isotype?

A

IgG

85
Q

What does IgG do?

A
  • Fixes complement
  • Crosses the placenta
  • Opsonizes bacteria
  • Neutralizes bacterial toxins & viruses
86
Q

What does IgG do when it crosses the placenta?

A

Provides infants w/ passive immunity

87
Q

What does IgA do?

A

Prevents attachment of bacteria & viruses to mucous membranes; does not fix complement

88
Q

Is IgA a monomer or a dimer?

A

Monomer in circulation

Dimer when secreted

89
Q

How does IgA cross epithelial cells?

A

Transcytosis

90
Q

Where is IgA found?

A

Secretions (tears, saliva, mucus) & early breast milk (colostrum)

91
Q

What does IgA pick up?

A

Secretory component from epithelial cells before secretion

92
Q

What does IgM do?

A

Fixes complement but does not cross the placenta

93
Q

When is IgM produced?

A

In 1° (immediate) reponse to an Ag

94
Q

Where is the Ag receptor for IgM?

A

Surface of B cells

95
Q

What is the structure of IgM?

A

Monomer on B cell or pentamer

96
Q

What does the shape of an IgM pentamer allow?

A

Efficiently trap free Ags out of tissue while humoral response evolves

97
Q

What is the function of IgD?

A

Unclear

98
Q

Where is IgD found?

A

Surface of many B cells & in serum

99
Q

What does IgE do?

A
  • Binds mast cells & basophils
  • Cross-links when exposed to allergen
  • Mediating immediate (type I) hypersensitivity through release of inflam mediators suchs as histamine
100
Q

What does IgE mediate?

A

Immunity to worms by activating esinophils

101
Q

Where is the lowest concentration of IgE?

A

In serum

102
Q

What are Thymus-independent Ags?

A

Ags lacking a peptide component; cannot be presented by MHC to T cells

103
Q

What do Thymus-independent Ags do?

A

Stim release of Abs & do not result in immunologic memory

104
Q

What are Thymus-independent Ags?

A

Ags containing a protein component

105
Q

How does class switching & immunologic memory w/ Thymus-dependent Ags occur?

A

Result of direct contact of B cells w/ Th cells

Immunology (7 decks)

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