1.5.2 Humoral Effector Mechanisms

Question 1

What is an antigenic shift?

Answer 1

Mutation of epitopes so that antibodies can no longer bind

Question 2

What are characteristics of immunogens?

Answer 2

These are greater than 10kDa, able to elicit an immune response w/o help

Question 3

What is a hapten?

Answer 3

A small antigen that must be bound to a large molecule to elicit an immune response

Question 4

Where are plasma cells concentrated?

Answer 4

These are concentrated in the bone marrow and medulla of lymph nodes

Question 5

How are antibodies transported?

Answer 5

By blood

Question 6

What antibody classes areinvolved in neutralization of toxins?

Answer 6

IgM, IgG and IgA

Question 7

What is the mechanism by which antibodies neutralize viruses and toxins?

Answer 7

Bind viruses and prevent attachment to cells and bind toxins and prevent it from binding receptors on cells

Question 8

What antibody classes are involved in opsonophagocytosis?

Answer 8

IgM and IgG

Question 9

What is the mechanism by which antibodies carry out opsonophagocytosis?

Answer 9

These coat the microbe with antibody. IgG-Ag complexes or complement bind macrophages and neutrophils via Fc-gamma-R or complement receptors and induce phagocytosis; induces ROS, NO, and proteolytic enzymes

Question 10

What is the major site for phagocytosis?

Answer 10

Spleen

Question 11

Phagocytosis is the major mechanism against what foreign pathogen?

Answer 11

Encapsulated bacteria

Question 12

What is the class of antibody that is involved in antibody-dependent cellular toxicity?

Answer 12

IgG

Question 13

What is the mechanism of antibody-dependent cellular toxicity?

Answer 13

IgG-Ag complexes bind to Fc-gamma-R on NK cells. The NK cells release perforin and granzyme B

Question 14

What antibody class is most involved with eosinophils and mast cells?

Answer 14

IgE

Question 15

What is the role of IgE and eosinophils?

Answer 15

These bind to Fc-epsilon-R and work against helminths and have a role in asthma

Question 16

What antibodies classes are involved in mucosal immunity?

Answer 16

IgA and IgM - IgA production is induced by TGF-beta produced in mucosal-associated lymph tissue

Question 17

What are some mechanisms of the immune system in the gut?

Answer 17

The villi drain into the mesenteric lymph node

M cell - transports antigens across intestinal wall and brings it to the peyers patch

Question 18

What are the characteristics of parenteral polio vaccines?

Answer 18

Intermuscular; Induces serum IgG; Neutralizes virus in blood; Protective no CNS infection; does not block viral entry and replication; permits carrier state

Question 19

What are the characteristics of oral polio vaccines?

Answer 19

Oral; Induces secretory IgA; neutralizes virus in GI tract; blocks viral entry and replication in gut; does not permit carrier state

Question 20

What is the mechanism of fetal and neonatal immunity?

Answer 20

FcRn binds free IgG and transports it across the placenta

Question 21

Is hypogammagloblinemia normal during infancy

Answer 21

Yes

Question 22

What are the major characteristics of the complement system?

Answer 22

effector system of Innate and Adaptive immunity; more than 25 serum proteins with biological activity; effects are mediated directly by peptides or through complement receptors

Question 23

What is the key step in the activation of the complement system?

Answer 23

formation of a C3 convertase

Question 24

What are the characteristics of the classical pathway?

Answer 24

IgM or IgG bound to antigen recruits C1q; C1q binds the Fc region of IgM or IgG; C1q recruits C1r and C1s to form the active enzyme that cleaves C2 and C4 (C3 convertase)

Question 25

What are the characteristics of the alternative pathway?

Answer 25

Spontaneous C3 hydrolysis leading to C3b on microbial charged surface; recruiting of factor B; Cleavage of Factor B by factor D; C3bB = C3 convertase; Factor P creates C3bBbP which is a very stable convertase leading to cleavage of C3 to C3a and C3b aids in amplification of all pathways

Question 26

What is the defining characteristic associated with the lectin pathway?

Answer 26

triggered by mannose-containing microbial carbohydrates

Question 27

What are the components of the C5 convertase?

Answer 27

C3 convertase and C3b

Question 28

What is the reaction the C5 convertase helps carry out?

Answer 28

Leads to conversion of C5 to C5a and C5b

Question 29

What is the role of C5a?

Answer 29

will be a key component in inflammation

Question 30

What is the role of C5b?

Answer 30

aids in the formation of the MAC complex

Question 31

What is the function of the MAC complex?

Answer 31

poly C-9 puts physical holes in the plasma membrane leading to cell lysis

Question 32

C3b and C4b carry out what function of the complement?

Answer 32

opsonization

Question 33

C5a carries out what function of the complement?

Answer 33

Inflammation - chemotaxis of neutrophils relies on C5a

Question 34

C3b and iC3b have what functions of the complement?

Answer 34

Solubilizing and clearance of immune complexes from circulation

Question 35

C3d is a co-activator for what cells?

Answer 35

B cells

Question 36

Mast cells, basophils, and SMCs have what receptor to work in anaphylaxis?

Answer 36

C5aR

Question 37

Phagocytes have what receptors for complement to aid in phagocytosis?

Answer 37

CR3 and CR4

Question 38

What is the receptor on erythrocytes what aids in clearance of soluble immune complexes?

Answer 38

CR1

Question 39

What are the characteristics of LAD-1?

Answer 39

CD18 deficiency leading to poor cell adhesion proteins. This leads to poor neutrophil adhesion and poor opsonophagocytosis using C3b or C4b

Question 40

C3 complement deficiency usually leads to?

Answer 40

Fatal susceptibility to infection

Question 41

C2 and C4 complement deficiency usually leads to?

Answer 41

Increased immune complex disease

Question 42

C9 deficiency leads to?

Answer 42

Neisseria

Question 43

When measuring complement what does ELISA do?

Answer 43

It measures the level of function for each protein in the pathway

Question 44

When measuring complement what does total hemolytic complement measure?

Answer 44

CH50 units. Measures the overall production of the complement

Question 45

What does an opsonophagocytic activity test do?

Answer 45

measuring the uptake of antibody-coated bacteria by neutrophils in the presence of fresh nonimmune serum

Question 46

The C1 inhibitor has what role?

Answer 46

a serine protease that dissociates C1qrs, which is involved in the classical pathway. This regulates the complement pathway

Question 47

What is hereditary angioedema?

Answer 47

unabated classical pathway activation leading to production of anaphylatoxins and resulting edema. Result from a loss of the C1 inhibitor

Question 48

What is the role of decay accelerating factor?

Answer 48

Preventing factor B from binding to C3b - blocking the formation of the C3 convertase (alternative pathway)

Question 49

What is the role of complement receptor 1?

Answer 49

Prevents Factor B from binding C3b - blocking the formation of the C3 convertase alternative pathway

Question 50

What is the role of Factor I?

Answer 50

degradation of C3b and C4b to iC3b and iC4b - blocking the formation of the C3 convertase

Question 51

What is the role of Factor H?

Answer 51

Binds C3b and acts as a co-factor for Factor I - blocking the formation of the C3 convertase

Question 52

What is the role of C4b binding protein?

Answer 52

Binds C4b - blocking the formation of the C3 converstase

Question 53

What is paroxysmal nocturnal hemaglobinuria?

Answer 53

Deficiency in enzyme that creates the glycolipid anchor that tethers DAF and MCP to membrane. Sporadic hemolysis due to spontaneous C3 activation on membranes of RBCs

Question 54

Homologous restriction factor does what?

Answer 54

Blocks MAC

Question 55

What is the role of anaphylatoxin inhibitor?

Answer 55

Cleaves and inactivates C3a, C4a and C5a

Question 56

What is the role of the S protein?

Answer 56

blocks MAC by attaching C5b678 to C9

Question 57

What is a reason the xenotransplantation is difficult?

Answer 57

Transplanting organs from pigs has problems because pig complement reg proteins do not regulate human complement