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Lymphocytes Flashcards

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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
What dz is HLA-DR3 assoc w/?
DM I & Grave's dz
26
What dz is HLA-DR4 assoc w/?
Rheumatoid arthritis & DM I
27
What dz is HLA-DR5 assoc w/?
Pernicious anemia→ B12 def Hashiomoto's thyroiditis
28
What do Natural Killer cells do?
Use Perforin & granzymes to induce apoptosis of virally infected cells & tumor cells
29
NK cells are the only lymphocyte member of the ____ \_\_\_\_ \_\_\_\_.
Innate immune system
30
What is NK cell activity enhanced by?
* IL-2 * IL-12 * IFN-ß * IFN-alpha
31
When are NK cells induced?
To kill when exposed to a nonsepcific activation signal on target cell &/or to an absence of class I MHC on target cell surface
32
What are the B cell functions?
Make Ab
33
What does Ab do?
* Opsonize bacteria * Neutralize viruses (IgG) * Activate complement (IgG, IgM) * Sensitize mast cells (IgE)
34
What does IgE respond to?
Allergy Type I hypersensitivity
35
What does IgG respond to?
Cytotoxic (type II) & Immune complex (type III) hypersensitivity
36
What are B cells involved in?
Hyperacute & humorally mediated acute & chronic organ rejection
37
What are the functions of CD4+ T cells?
Help B cells make Ab & produce cytokines to activate other cells of immune system
38
What is the function of CD8+ T cells?
Kill virus-infected cells directly
39
What are T cells involved in?
Delayed cell-med hypersensitivity (type IV) Acute & chronic cellular organ rejection
40
Where does Positive selection happen?
Thymic cortex
41
What is Positive selection?
T cells expressing TCRs capable of binding surface self MHC molecules survive
42
Where does Negative selection happen?
Thymic medulla
43
What is Negative selection?
T cells expressing TCRs w/ high affinity for self Ag's undergo apoptosis
44
What causes T & B cell activation?
Antigen-presenting cells (APCs)
45
What are the APCs?
* Dendrite cell * Macrophage * B cell
46
What is the only APC that can activate naive T cell?
Dendrite cell
47
How many signals are required for T & B cell activation& B cell class switching?
Two signals
48
What is the 1st step of Naive T cell activation?
Foreign body is phagocytosed by dendritic cell
49
What is the 2nd step of naive T cell activation?
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
What is the 3rd step in naive T cell activation?
"Costimulatory signal" is given by interaction of B7 & CD28 (signal 2)
51
What is the 4th step in naive T cell activation?
Th cell activates & produces cytokines. Tc cell activates & is able to recognize & kill virus-infected cell
52
What is the 1st step of B cell activation & class switching?
Helper T cell activation same as naive T cell activation
53
What is the 2nd step of B cell activation & class switching?
B cell receptor-med endocytosis; foreign Ag is presented on MHC II & recognized by TCR on Th cell (signal 1)
54
What is the 3rd step of B cell activation & class switching?
CD40 receptor on B cell binds CD40 ligand on Th cell (signal 2)
55
What is the 4th step of B cell activation & class switching?
Th cell secretes cytokines that determine Ig class switching of B cell. B cell activates & undergoes class switching, affinity maturation & Ab production
56
What do Th1 cells secrete?
IFN-gamma
57
What do Th2 cells activate?
Macrophages
58
What are Th1 cells inhibited by?
IL-4 & IL-10 (from Th2 cell)
59
What do Th2 cells secrete?
IL-4, IL-5, IL-10, IL-13
60
What do Th2 cells recruit?
Eosinophils for parasite defense & promotes IgE production by B cells
61
What are Th2 cells inhibited by?
IFN-gamma (from Th1 cell)
62
What is Macrophage-lymphocyte interaction?
Activated lymphocytes (release INF-gamma) & macrophages (release IL-1, TNF-alpha) stim one another
63
Helper T cells have ____ which binds to ____ on \_\_\_
CD4, MHCII, APCs
64
What do Cytotoxic T cells do?
Kill virus-infected, neoplastic & donor graft cells by inducing apoptosis
65
What do Cytotoxic T cells release?
Cytotoxic granules containing performed proteins
66
What is perforin?
Helps to deliver the content of granules into target cell
67
What is granzyme?
A serine protease, activates apoptosis inside target cell
68
What is granulysin?
Antimicrobial, induces apoptosis
69
What does CD8 on cytotoxic T cells bind to?
MHC I on virus-infected cells
70
What do Regulatory T cells do?
Help maintain specific immune tolerance by suppressing CD4 & CD8 T-cell effector functions
71
What do regulatory T cells express?
CD3, CD4, CD25 (alpha chain of IL-2 receptor) cell surface makers
72
What do activated regulatory T cells produce?
Anti-inflammatory cytokines like IL-10 & TGF-ß
73
What do the variable part of L & H chains on Ab recognize?
Antigens
74
What does the Fc portion of IgM & IgG do?
Fixes complement
75
What does the Heavy chain of Ab do?
Contributes to Fc & Fab fractions
76
What does the Light chain of Ab do?
Contributes only to Fab fraction
77
What is the Fab fraction of an Ab?
* Ag-binding fragment * Determines idiotype: unique Ag-binding pocket; only 1 antigenic specificity expressed per B cell
78
What is the Fc fraction of an Ab?
* Constant * Carboxy terminal * Compliment binding at CH2 (IgG + IgM only) * Carbohydrate side chains * Determines isotype (IgM, IgD, etc)
79
What is Ab diversity generated by?
* 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
What do mature B lymphocytes express?
IgM & IgD on their surfaces
81
How can mature B lymphocytes differentiate?
Isotype switching into plasma cells that secrete IgA, IgE or IgG
82
What is isotype switching?
Gene rearrangement mediate by cytokines & CD40 ligand
83
What is IgG?
Main Ab in 2° (delayed) response to an Ag
84
What is the most abundant Ig isotype?
IgG
85
What does IgG do?
* Fixes complement * Crosses the placenta * Opsonizes bacteria * Neutralizes bacterial toxins & viruses
86
What does IgG do when it crosses the placenta?
Provides infants w/ passive immunity
87
What does IgA do?
Prevents attachment of bacteria & viruses to mucous membranes; does not fix complement
88
Is IgA a monomer or a dimer?
Monomer in circulation Dimer when secreted
89
How does IgA cross epithelial cells?
Transcytosis
90
Where is IgA found?
Secretions (tears, saliva, mucus) & early breast milk (colostrum)
91
What does IgA pick up?
Secretory component from epithelial cells before secretion
92
What does IgM do?
Fixes complement but does not cross the placenta
93
When is IgM produced?
In 1° (immediate) reponse to an Ag
94
Where is the Ag receptor for IgM?
Surface of B cells
95
What is the structure of IgM?
Monomer on B cell or pentamer
96
What does the shape of an IgM pentamer allow?
Efficiently trap free Ags out of tissue while humoral response evolves
97
What is the function of IgD?
Unclear
98
Where is IgD found?
Surface of many B cells & in serum
99
What does IgE do?
* Binds mast cells & basophils * Cross-links when exposed to allergen * Mediating immediate (type I) hypersensitivity through release of inflam mediators suchs as histamine
100
What does IgE mediate?
Immunity to worms by activating esinophils
101
Where is the lowest concentration of IgE?
In serum
102
What are Thymus-independent Ags?
Ags lacking a peptide component; cannot be presented by MHC to T cells
103
What do Thymus-independent Ags do?
Stim release of Abs & do not result in immunologic memory
104
What are Thymus-independent Ags?
Ags containing a protein component
105
How does class switching & immunologic memory w/ Thymus-dependent Ags occur?
Result of direct contact of B cells w/ Th cells

Immunology (7 decks)

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