Effector mechanisms of humoral immunity Flashcards
(76 cards)
1
Q
Effector functions of antibodies
A
- neutralization of microbes/toxins
- opsonization/phagocytosis of microbes
- antibody-dependent cellular cytotoxicity
- complement: phagocytosis, inflammation, lysis
2
Q
Main function of antibodies
A
neutralize and eliminate infectious microbes and microbial toxins
3
Q
antibodies are produced by what ?
A
- plasma cells in peripheral (secondary) lymphoid
- inflamed tissues
- bone marrow
4
Q
where do antibodies perform their effector functions ?
A
distant from their production
5
Q
effector functions of antibodies are mediated by …
A
Fc regions of Ig molecules & different Ig heavy chain isotypes
6
Q
the effector functions of antibodies that are mediated by the Fc regions are triggered by what?
A
binding of antigens to the variable regions
7
Q
mechanism of polio vaccine
A
neutralization of virus by IgG or by mucosal IgA antibody
8
Q
mechanism of tetanus, diphtheria vaccine
A
neutralization of toxin by systemic IgG antibody
9
Q
mechanism of hep A and hep B vaccine
A
neutralization of virus by mucosal IgA or systemic IgG antibody
10
Q
mechanism of pneumococcal pneumonia, haemophilus influenzae, neisseria meningitidis vaccine
A
opsonization & phagocytosis mediated by IgM and IgG antibodies, directly or secondary to complement activation
11
Q
Functions of IgG
A
- opsonization of antigens for phagocytosis via macrophages/neutrophils
- activation of classical complement
- antibody-dependent cell-mediated cytotoxicity by NK cells
- neonatal immunity (maternal antibodies cross placenta)
- feedback inhibition of B cell activation
- neutralization of microbes
12
Q
Function of IgM
A
activation of the classical pathway of complement
13
Q
Functions of IgA
A
- Mucosal immunity through the lumen of the gastrointestinal and respiratory tracts
- Neutralization of microbes and toxins in lumens of mucosal organs
14
Q
Functions of IgE
A
- Mast cell degranulation (immediate hypersensitivity reactions)
- Eosinophil-mediated defense against helminths
15
Q
FcRN receptor
A
pH-dependent that has an increased half-life and transports maternal IgG to fetus
16
Q
FcγRIIA, FcγRIIB & FcγRIIC receptors has ___ affinity for immunoglobulin
A
Low
17
Q
Inhibitory Fcy receptor (w/ low affinity)
A
FcγRIIB
18
Q
Activating Fcy receptors
A
- FcyRI
- FcyRIIA/C
- FcyRIII-A
- FcryRIII-B
19
Q
Which activating Fcy receptor have high affinity for immunoglobulin?
A
FcyRI
20
Q
Which activating Fcy receptor have low affinity for immunoglobulin?
A
- FcyRIIA/C
- FcyRIII-A
3.FcγRIII-B
21
Q
FcyRI activates
A
CD64
22
Q
FcyRIIA/C activates …
A
CD32
23
Q
FcyRIII-A and FcyRIII-B activates
A
CD 16
24
Q
FcγRIIB inhibits
A
CD32
25
Select all that apply: Cell distribution of FcyRI (CD64)
A. Macrophages
B. Neutrophils
C. Eosinophils
D. Dendritic cells
E. Mast cells
F. Platelets
G. B cells
H. NK cells
I: Basophils
J: Langerhans cells
I: Monocytes
Macrophages, neutrophils and Eosinophils (MEN)
26
Select all that apply: Cell distribution of FcyRIIA (CD32)
A. Macrophages
B. Neutrophils
C. Eosinophils
D. Dendritic cells
E. Mast cells
F. Platelets
G. B cells
H. NK cells
I: Basophils
J: Langerhans cells
I: Monocytes
Platelets, Eosinophils, Neutrophils, Dendritic cells and Macrophages (PENDM)
27
Select all that apply: Cell distribution of FcyRIIB (CD32)
A. Macrophages
B. Neutrophils
C. Eosinophils
D. Dendritic cells
E. Mast cells
F. Platelets
G. B cells
H. NK cells
I: Basophils
J: Langerhans cells
I: Monocytes
B cells, Macrophages, Dendritic cells (BMD)
28
Select all that apply: Cell distribution of FcyRIIC (CD32)
A. Macrophages
B. Neutrophils
C. Eosinophils
D. Dendritic cells
E. Mast cells
F. Platelets
G. B cells
H. NK cells
I: Basophils
J: Langerhans cells
I: Monocytes
NK cells, Neutrophils and Macrophages (NKNM)
29
Select all that apply: Cell distribution of FcyRIIIA (CD16)
A. Macrophages
B. Neutrophils
C. Eosinophils
D. Dendritic cells
E. Mast cells
F. Platelets
G. B cells
H. NK cells
I: Basophils
J: Langerhans cells
I: Monocytes
NK cells, Macrophages, Dendritic cells (NKMD)
30
Cell distribution of FcyRIIIB (CD16)
Neutrophils
31
Affinity of FcεRI
High; binds IgE
32
Affinity of FcεRII (CD23)
Low
33
Affinity of FcaR (CD89)
Low
34
Select all that apply: Cell distribution of FcεRI
A. Macrophages
B. Neutrophils
C. Eosinophils
D. Dendritic cells
E. Mast cells
F. Platelets
G. B cells
H. NK cells
I: Basophils
J: Langerhans cells
I: Monocytes
Mast cells, basophils, eosinophils (Masbephils)
35
Select all that apply: Cell distribution of FcεRII (CD23)
A. Macrophages
B. Neutrophils
C. Eosinophils
D. Dendritic cells
E. Mast cells
F. Platelets
G. B cells
H. NK cells
I: Basophils
J: Langerhans cells
I: Monocytes
B cells, eosinophils, Langerhans cells (BLangEphil)
36
Select all that apply: Cell distribution of FcaR (CD89)
A. Macrophages
B. Neutrophils
C. Eosinophils
D. Dendritic cells
E. Mast cells
F. Platelets
G. B cells
H. NK cells
I: Basophils
J: Langerhans cells
I: Monocytes
Neutrophils, Eosinophils, Monocytes (NEM)
37
function of FcyRI (CD64)
phagocytosis; activation of phagocytes
38
function of FcyRIIA (CD32)
phagocytosis; cell activation
39
function of FcyRIIB (CD32)
feedback inhibition of various cellular responses
40
function of FcyRIIC (CD32)
phagocytosis; cell activation
41
function of FcyRIIIA (CD16)
antibody dependent cell mediated cytotoxicity
42
function of FcyRIIIB (CD16)
phagocytosis (inefficient)
43
function of FcεRI
cell activation (degranulation)
44
function of FcεRII (CD23)
unknown
45
function of FcaR (CD89)
cell activation
46
What is the role of Fc receptors in antibody-coated (opsonized) particles?
They stimulate the microbicidal activities of phagocytes
47
True or False: Antibodies block the infectivity of microbes by binding to the microbes and sterically hindering interactions with cellular receptors.
True
48
18. True or False: Attachment of antigen-complexed Ig to phagocyte Fc receptors does not deliver signals that stimulate the microbicidal activities of phagocytes.
False
49
Which statement is true regarding the role of antibodies in defense against extracellular microbes and microbial toxins?
a. Antibodies destroy microbes by directly attacking them.
b. Antibodies block the infectivity of microbes and toxins by binding to them and preventing interactions with cellular receptors.
Antibodies block the infectivity of microbes and toxins by binding to them and preventing interactions with cellular receptors.
50
Which statement is false regarding Fc receptors and antibody-coated particles?
a. Fc receptors stimulate the microbicidal activities of phagocytes.
b. Different Fc receptors bind antibodies with the same affinities.
c. Fc receptors are specific for different subclasses of antibodies.
Different Fc receptors bind antibodies with the same affinities.
51
Which of the following are true regarding the production of antibodies that protect against infection? (Select all that apply)
a.They are produced only upon the first exposure to microbial antigen
b.They may be generated by long-lived antibody-secreting cells
c.They can be produced by reactivation of memory B cells
B. They may be generated by long-lived antibody-secreting cells
C. They can be produced by reactivation of memory B cells
52
Which arm of the adaptive immune system is primarily responsible for defense against extracellular microbes and microbial toxins?
humoral immunity
53
What is the common endpoint for all three major pathways of complement activation?
Cytolysis
54
How are antibodies involved in blocking the infectivity of microbes and toxins?
By binding to and hindering interactions of microbes with cellular receptors
55
True or False: The three major pathways of complement activation converge on a common pathway involving the formation of a membrane pore after the proteolytic cleavage of C5.
True
56
why complement activation need to be regulated?
1. Low-level complement activation goes on spontaneously and the result can damage normal cells and tissues.
2. degradation products of complement proteins can diffuse to adjacent cells and injure them.
57
Different regulatory mechanisms of complement activation
1. Inhibition of the formation of C3 convertases in the early steps of complement activation.
2. Break down and inactivate C3 and C5 convertases.
3. Inhibition of the formation of the MAC in the late steps of the complement pathway.
58
Which biologic functions are associated with the complement system? (Select all that apply)
a. Opsonization of organisms and immune complexes
b. Activation of inflammatory cells by proteolytic fragments
c. Cytolysis mediated by MAC formation
d. Enhancement of cellular immune responses
e. Solubilization and clearance of immune complexes
a. Opsonization of organisms and immune complexes
b. Activation of inflammatory cells by proteolytic fragments
c. Cytolysis mediated by MAC formation
e. Solubilization and clearance of immune complexes
59
Which pathway of complement activation is initiated by circulating lectins binding to carbohydrates on pathogens?
c. Lectin pathway
60
Which is a principal mechanism of innate immunity against extracellular bacteria?
a. Phagocytosis
b. Cell-mediated immunity
c. Cytotoxic T lymphocytes
Phagocytosis
61
What is the major protective immune response against intracellular bacteria?
a. Innate immune response
b. B cell activation
c. Humoral immunity
d. Cell-mediated immunity
Cell-mediated immunity
62
T/F Hereditary angioneurotic edema is caused by failure to regulate complement activation.
true
63
PNH missing ...
DAF &CD59
64
t/f PNH increased sensitivity to complement lysis
true
65
characteristic of PNH
hemoglobinuria (loss of iron)
66
treatment of PNH
1. Transfusion of packed red blood cells can replace lost cells.
2. Androgens and recombinant erythropoietin are commonly used to accelerate erythropoiesis.
3. Thrombotic complications are reduced by standard therapy, including heparin and maintenance doses of common anticoagulants.
4. Iron loss is corrected by the administration of supplemental iron.
5. To reduce complement activation, eculizumab can be used to block the activation of C5 and the generation of the MAC
67
t/f Paroxysmal nocturnal hemoglobulinuria (PNH) is caused by lack of membrane-bound complement inhibitors.
true
68
true/false Complement deficiencies in C2, alternative pathway components, or the membrane attack complex (MAC) increase the risk of life-threatening neisserial infections.
true
69
Hereditary angioneurotic edema (HANE) is caused by
C1 INH deficiency
70
treatment of HANE
Oral androgens, anabolic steroids, and antifibrinolytic agents
71
treatment of HANE in case of acquired C1 INH deficiency
glucocorticosteroids
72
alternative pathway activated by ....
microbial surfaces in the absence of antibody
73
classical pathway activated by ....
antigen-antibody complexes
74
lectin pathway activated by ....
circulating lectins binding to carbohydrates on pathogens
75
Individuals with a .... deficiency usually have recurrent infections of the respiratory tract, gut, and
skin.
C3
76
t/f Life-threatening meningitis is associated with defects in properdin, factor H, factor I, and the
complement MAC.
true, which is why meningococcal vaccination is indicated to create high levels of protective
antibodies.
