Unit 4 - Humoral Immunity Flashcards
(119 cards)
1
Q
What do lymphatic vessels contain?
A
Carry lymphatic fluid instead of blood (likes veins and arteries)
2
Q
True or False:
Organs are tightly packed with leukocytes
A
True
3
Q
What is the (believed) role of tonsils?
A
Entrap pathogens, rich in leukocytes
4
Q
What is the role of the spleen? Will you find leukocytes there?
A
Filters blood
- rich in leukocytes!
5
Q
How is the humoral system different than the cell-mediated system?
A
Humoral immune components are dissolved in extracellular fluid
6
Q
Identify which of the following is cell-mediated or humoral (neutrophil, complement, antibodies, cytotoxic t-cells)
A
Humoral = complement + antibodies Cell-mediated = neutrophil + cytotoxic t-cells
7
Q
What are clonal cells?
A
Cells that are GENETICALLY identical
8
Q
True or False:
Bacterial cells are clones
A
True
9
Q
What is the name of the process that occurs that makes some lymphocytes no longer genetically identical?
A
VDJ recombination
10
Q
What is the name of the process that occurs after VDJ recombination?
A
Class switching
11
Q
True or False:
Every cell recognizes only a single, unique epitope
A
True
12
Q
What recognizes the epitopes of antigens?
A
Receptors of lymphocytes
13
Q
Are antibodies made when an antigen is contacted?
A
No
- B-cells already have antibodies present on their outside prior to an infection
- They DO undergo clonal expansion when the specific B-cells contacted their specific antigen
14
Q
What is an antibody?
A
A secreted B-cell receptor
15
Q
What are the components of the antibody?
A
- Antigen binding site
- Light chain (small polypeptide)
- Heavy chain (large polypeptide)
- light chain and heavy chain are bound by sulfide bond
16
Q
What is special about the antigen binding site?
A
Specifically shaped to bind to a specific epitope
17
Q
Define affinity
A
The strength with which an antibody (or other receptor) binds its epitope
18
Q
Why is the antigen binding site regarded as hypervariable?
A
The shape varies from one antibody to another
19
Q
What is the variable (V) segment of the antibody?
A
The antigen binding site (at the tips, “hands”)
20
Q
What is the constant segment of the antibody?
A
The area the specifies the antibody function
- made up of the light and heavy chains
21
Q
What is the fragment of antigen binding site (Fab)?
A
Made up of:
- The antigen binding site
- The light chain
- The top piece of the heavy chain
22
Q
What is the fragment crystallizable (Fc) segment of the antibody?
A
It connects it to the B-cell
- made up of the bottom half of the heavy chain
23
Q
How can antibodies by split at their hinge region?
A
By some proteases
- ex: papain protease
24
Q
During a primary infection, is the antibody response fast or slow?
A
Slow
25
What 3 things happen to B-cell during an infection?
1. Clonal expansion
2. Class switching
3. Memory cells form
26
What is another name for the primary infection?
Sensitization
27
Why does a secondary immune response happen faster?
Memory B-cells promote a faster antibody response
28
True or False:
| Naive B-cells are in greater number than memory B-cells
False
| - Memory B-cells are in greater number than naive B-cells
29
True or False:
| Antibodies switch from IgM to a more effective class, IgG
True
30
True or False:
| Plasma cells still have their antibodies
False
31
True or False:
| Memory B-cells still have their antibodies
True
32
True or False:
| Every antibody starts off as an IgG
False
| - every antibody starts off as an IgM
33
During a primary response, what is the class of antibody from plasma cells that is first created?
IgM
34
True or False:
| There is a latent period in the secondary infection
False
- no latent period b/c memory cells from the primary infection still exist
- they mount an immediate response
35
What is the difference between the primary and secondary infections?
```
First = latent period; first IgM and then IgG (peaks at separate times) titer tapers back to low levels
Second = no latent period; IgG response is MUCH stronger and faster compared to primary infection; antibody levels are sustained for several weeks
```
36
What is another name for plasma B-cells?
Effector cells
37
What segment of the antibody give rise to distinct antibody classes?
Fc
| = fragment crystallizable
38
What is the function of IgM?
Primary immune response
| - B-cell receptor
39
What is the function of IgD?
Undefined
| - B-cell receptor
40
What is the function of IgA? Where is it found?
Prevents adhesion
| - found in breastmilk and mucosal surfaces
41
What is the function of IgG?
Long-lasting immune response
42
What is the function of IgE?
Allergic response
| - also protects against parasites
43
What kind of antibody class will we have, if the antibody class DOESN'T change?
IgM
44
How does B-cell class switching occur?
1. Genes in HEAVY chain of an IgM expressing B-cell
2. Removal of DNA segment by enzyme activity
3. Non-homologous end joining of DNA at switch regions
4. Genes in HEAVY chain will become whichever class gene is expressed FIRST after the VDJ segment
45
The following is a transcript of an IgM:
VDJ ... M, G, A, E, D, M
And the portion, MGA is deleted. What class will this antibody become?
Class E = IgE
| VDJ ... E, D, M will be leftover
46
True or False:
| Once a B-cell has switched classes, it cannot switch back
True
| - If a B-cell switches from a IgM to a IgG, it cannot switch back
47
How are IgM structed when they are on the B-cell, and how are they structured when they are expressed/secreted?
On B-cell = monomeric
| Secreted = pentameric
48
True or False:
| IgM has the ability to fix complement
True!
| - Complement will bind to IgM
49
When an IgM goes from monomeric to pentameric, what is the joining factor?
A "J" chain
50
What antibody is secreted as part of the primary response?
IgM
51
What two functions of antibodies (there are 4 in total) goes IgM participate in?
1. Agglutination
| 2. Complement fixation
52
If IgM forms a pentomer once it is secreted (sIgM), how many binding sites will it have?
10!
53
What kind of antibody is used in blood typing? Why?
IgM
| - because the precipitate will form and "fall out" of the solution
54
What does the complement system promote?
Chemotaxis, inflammation, opsonization, and formation of membrane attack complex
55
True or False:
| IgM antibodies induce chemotaxis
False!
| - they activate (or are bound to) the complement system, which DOES have chemotactic factors
56
True or False:
| IgM antibodies do not participate in the lysing of cells
True
| - IgM antibodies activate (or are bound to) the complement system, which forms the MAC (membrane attack complex)
57
What do we need to know about IgD?
That it exists!
| - the function of IgD is unclear, might be similar to IgM
58
What does IgA form when it is secreted?
Dimer
| - two IgA molecule will join together by a "J" chain
59
What virulence factor does IgA prevent?
Adherence!
60
Where is IgA predominantly found?
Seromucosal secretions
| - saliva, colostrum, breastmilk, tracheobronchial and genitourinary secretions
61
What is the greek letter that is associated with IgM?
µ = IgM
62
What is the greek letter that is associated with IgA?
α = IgA
63
What is the greek letter that is associated with IgE?
ε = IgE
64
What is the greek letter that is associated with IgG?
γ = IgG
65
What is the greek letter that is associated with IgD?
δ = IgD
66
Why are IgA antibodies not destroyed by stomach acid (like the antibodies found in breast milk)?
Part of the Fc-A receptor remains BOUND to the sIgA dimer as a "secretory component"
- makes sIgA resistant even to stomach acid
67
What segment of the IgA antibody is involved in neutralization?
Fab
| - the VDJ section and the light chain, and the top portion of the heavy chain
68
Explain how IgA neutralizes toxins
IgA prevents binding to the surface of the cell by binding to the epitope on the antigen (toxin)
69
What binds to GP120 and prevents it from contacting with the HIV receptor CD4?
mAB B12
70
Which antibody is involved in the secondary immune response?
IgG
71
What antibody makes up 80% of circulating immunoglobulins?
IgG
72
True or False:
| IgG's are able to cross the placenta and give passive immunity to the fetus
True
73
What functions (of antibodies) are IgG's able to do?
All 4 of them!
- Neutralization
- Opsonization
- Complement Activation
- Agglutinate
74
How does IgG participate in opsonization?
Directly = phagocytes are more effective in capturing extracellular antigens when they are coated with antibodies such as IgG
75
What kind of receptors are on the phagocytes that bind to IgG?
Fc-gamma receptors
76
Mom passes IgG to baby in utero, but what are the first three antibodies that the baby makes on it's own?
1. IgM
2. IgG
3. IgA
77
Under what two conditions are IgE levels elevated?
1. Type 1 hypersensitivity
| 2. Parasitic infections
78
What is a Type 1 hypersensitivity?
Allergic response to re-exposure to antigen
| - mast cells and basophils release histamine)
79
True or False:
| Mast cells could have IgEs deposited on them
True
| - and if they are stimulated, they will cause the cell to degranulate and release histamine
80
True or False: Either mast cells or eosinophils could be bound to the FC-E receptor
True
81
What is the most common antibody?
IgG
82
What is the least common antibody?
IgE
| - because they are already stuck to mast cells
83
Where is the FC-gamma receptor located?
On the phagocyte
| - IgG is an opsinin
84
Where are Fc-alpha receptors located?
On epithelial cells, supports secretion
85
Where are Fc-epsilon receptors located?
On basophils or mast cells
| - stimulates degranulation
86
True or False:
| Fc segment of antibody determines the antibody role
True
87
Review what the roles/function are of the major 5 types of antibodies.
```
IgM = primary response
IgG = major antibody of secondary response
sIgA = secretory component, seromucosal secretions
IgE = allergy, parasite
```
88
If an APC (antigen presenting cell) presents an antigen to a T-helper cell, what could the response be?
1. Humoral (antibodies)
| 2. Cell-mediated (cytotoxic t-cells)
89
How do macrophages activate T-helper cells (TH-0 cells)?
With IL-1
90
What happens to TH-0 cells if they ONLY secrete IL-2?
Cell-mediated response
- TH-1 cells
- CYTOTOXIC T-CELLS
91
What happens to TH-0 cells if they secrete IL-2 and IL-4?
Humoral response
- TH-2 cells
- Activate B-cells
92
What are the steps of helper T-cell activation in the humoral response (and B-cell activation)?
1. Dendritic cells eats and presents an antigen
2. Dendritic cell secretes IL-1 (stimulates helper T-cell)
3. B-cell would have eaten same antigen and presented it to helper T-cell
4. Helper T-cell secretes IL-2 and IL-4, changes it to TH-2 cell
5. TH-2 cell activates B-cell
6. Activated B-cell antibodies undergo class switching (IgM to IgG)
7. Plasma B-cells and Memory B-cells are formed
93
Are the vast majority of antibodies produced from T-cell dependent or independent cells?
T-cell dependent
94
If you remove the thymus and an HIV infection prevents the formation of mature T-helper cells, can T-cells still be made?
Yes!
| - T-cell independent ones can still be made
95
Define serology
Branch of immunology involving testing serum
96
What do you typically test for in serum?
- antibodies
- antigens
- cytokines
97
In an agglutination / precipitation test, if the antigen is NOT bound to a microbe, what will happen to it?
It will precipitate
98
What was the agglutination/precipitation test for, that was developed over 100 years ago?
Typhoid fever
= "Widal Test"
- caused by salmonella typhi
99
How do we make polyclonal antibodies?
1. Inject animals with antigen
2. Collect blood and isolate the serum
3. Purify the IgG
100
What are the pros and cons of polyclonal antibodies?
```
Pros = cheap; able to produce large amounts; against ALL the epitopes of the protein
Cons = there could be cross-reactivity (serum sickness)
```
101
How do we make monoclonal antibodies?
1. Remove spleen from immunized mice
2. Fuse spleen cells with myeloma cancer cells
3. Select a single cell (one cell = one epitope)
- it is LESS likely to react with your own cells than compared to polyclonal
102
What is immunostaining?
Binding stain or fluorescent molecule to an antibody
| - then cells bearing the antigen will glow!
103
What is the antigen highly expressed in some breast cancer cells that we are able to stain for?
Epidermal growth factor (her2)
| = anti-her2 antibody conjugated to stain, allows us to visualize breast cancer cells under the microscope
104
What does flow cytometry measure?
The AMOUNT of antigen per cell
| - ability to count a large number of cells
105
What kind of test is used to count the amount of CD4+ cells in HIV/AIDS?
Flow Cytometry (FACS)
- counts AMOUNT of antigen per cell
- < 200 cell/ml = HIV/AIDS
106
What does ELISA stand for?
Enzyme-linked immunosorbent assay
107
What does ELISA measure?
Amount of antibody present
- an enzyme is conjugated to antibodies
- when antibody is present, the enzyme causes a color change
108
What is a classic example of an ELISA test?
An allergy test
- antigen in serum
- add in patient's serum + enzyme
- if it changes color, there is an allergy present
109
In direct ELISA, what is added first - the antibody or the antigen?
Antibodies
110
What is the order of the three things added to a direct ELISA?
1. Antibodies - wash off excess
2. Add patient serum with suspected antigen (antigen will bind with antibodies present in test)
3. Add 2nd antibody that is bound with an enzyme that will change color of solution if antigen is present
111
What is the order of the three things added to an indirect ELISA?
1. Add antigen
2. Add patient serum (if allergic, patient serum WILL have antibodies against antigen)
3. Add 2nd antibody that is bound to an enzyme that will change color if it binds to the Fc segment of the first antibody
112
What does Immunoblotting test for?
The size of proteins and the specific antigen is detected by immunostaining
113
What is the purpose of an agglutination test?
Rapid test for serum antibody
114
What is the purpose of elecrophoresis?
Separation by size
115
What is the purpose of immunostaining?
Detection of antigen on cell surface
116
What is the purpose of flow cytometry?
Amount of antigens per cell
| - number of antigen +ve cells
117
What is the purpose of ELISA?
Amount of antigen in a sample
118
What is the purpose of immunoblotting?
Visualizing a specific antigen
119
What is the home based pregnancy test based on?
ELISA
- enzyme-conjugate antibodies bind hCG
- induces color change
