Humoral Immunity

Question 1

Which immunoglobulin isotypes can cross the placenta?

Answer 1

IgG

Question 2

What complement protein subunit initiates the formation of the membrane attack complex?

Answer 2

C5b

Question 3

What are the polypeptide chains that make an antibody?

Answer 3

2 identical heavy chains

2 identical light chains

Question 4

What chromosome are the heavy chain genes on?

Answer 4

14

Question 5

What chromosome are the light chain genes on?

Answer 5

2 (kappa) and 22 (lambda)

Question 6

In early B-cell differentiation what are the bone marrow genes rearranged to generate?

Answer 6

Immunologlobulins

Question 7

Which comes first; the Ig heavy or light chain?

Answer 7

The heavy chain comes first

Question 8

What are the protective mechanisms of binding antibodies to anitgens?

Answer 8

Agglutination
Opsonization
Neutralization
Activation of complement 
Inflammation
Antibody-dependent cell-mediated cytotoxicity

Question 9

What does agglutination do?

Answer 9

Enhances phagocytosis and reduces the number of infectious units to be dealt with

Question 10

What does neutralization do?

Answer 10

Blocks adhesion of bacteria and viruses to mucosa and blocks active site of toxin

Question 11

What are the characteristics of follicular B cells??

Answer 11

T-dependent isotype-switched high affinity; long lived plasma cells

Question 12

What are the characteristics of marginal zone B cells?

Answer 12

T-independent (IgM); short lived plasma cells

Question 13

What are the characteristics of B-1 B cells?

Answer 13

T-independent (IgM); short lived plasma cells

CD5 positive

Question 14

What are T-independent antigens?

Answer 14

Polysaccharides, nucleic acids, lipids

Question 15

What are T-dependent antigens?

Answer 15

Protein antigens

Question 16

What are the secondary immune organs?

Answer 16

The lymph nodes and the spleen

Question 17

What is somatic hypermutation (SHM)?

Answer 17

Introduction of a single nucleotide substitution (point mutation)
Follows B-cell activation by an antigen
More common in the V chain of heavy chain (results in higher affinity)

Question 18

What is class switching?

Answer 18

Process by which an Ig changes class or isotype 
The antigenecity is preserved

Question 19

Where does class switches occur?

Answer 19

On the heavy chain

Question 20

When does class switching occur and what happens during it?

Answer 20

It occurs during the immune response and invovles the deletion of the C segment

Question 21

What are some of the factors in immunoglobulin diversity?

Answer 21

V(D)J recombination
Somatic hypermutation
Class switching
RAG1/RAG2
Base excision and repair

Question 22

What is hyper IgM syndrome?

Answer 22

Results from mutations affecting class switching which is rare
Decreases the IgG, IgA, IgE

Question 23

How do you treat hyper IgM syndrome?

Answer 23

IVIG, BMT

Question 24

Describe to me IgM;

Answer 24

A pentamer which is the first Ig made by a fetus and B cells
Expressed as membrane bound Ig
Opsonization (Fc receptor - phagocytes)

Question 25

Where is IgM present in the mother?

Answer 25

In colostrum (momma milk) to protect newly born

Question 26

Is IgM produced in secondary immune response?

Answer 26

Sometimes

Question 27

Tell me about IgG;

Answer 27

Major serum Ig and most abundant Major immunoglobulin of secondary immune response and in the extravascular spaces Involved in opsonization

Question 28

Which Igs fix complements;

Answer 28

IgM, IgG

Question 29

Explain the IgA;

Answer 29

Found in serum and body secretions, major secretory Ig on mucous surfaces

Question 30

Where is IgA present in the mom?

Answer 30

Colostrum and momma milk

Question 31

What about IgE?

Answer 31

Least common serum Ig which binds to basophils and mast cells

Question 32

What is IgE active in?

Answer 32

``` Allergic and hypersensitivity rxns Parasitic infection (helminths) and binds to Fc receptors on eosinophils ```

Question 33

Tell me about those IgD;

Answer 33

Found on membrane of mature B-cells and have a small presence in serum B cell surface Ig

Question 34

What does IgD do biologically?

Answer 34

Who knows

Question 35

Describe IgA1;

Answer 35

Monomeric and found in the blood and extracellular spaces

Question 36

Describe IgA2;

Answer 36

Dimeric and found in mucous and secretions

Question 37

What are the characteristics of the primary antibody response?

Answer 37

Usually 5-10 days, has a small peak response has more IgM than IgG and has a lower average antibody affinity yet more variable

Question 38

What are the characteristics of the second antibody response?

Answer 38

1-3 days, has a large peak response, relatively increases IgG and sometimes IgA and IgE when there is heavy chain isotype switching Higher average antibody affinity

Question 39

What is the process of opsonization and phagocytosis?

Answer 39

The C3b (C4b) binds to the microbe The C3b is recognized by a phagocyte C3b receptor Phagocytosis and microbe killing occurs

Question 40

What is the process of compliment-mediated cytolysis?

Answer 40

The C3b binds to a microbe activating the late components of complement There is a formation of the membrane attack complex (MAC) Osmotic lysis of microbe occurs

Question 41

What is the process of stimulation of inflammatory reactions?

Answer 41

Proteolysis of C3, C4 and C5 to release C3a, C4a and C5a Recruitment and activation of leukocytes by C5a, C3a and C4a Destruction of microbes by leukocytes

Question 42

What is the function of C2b?

Answer 42

Prokinin: Cleaved by plasmin -> Kinin -> Edema

Question 43

What is the function of C3a?

Answer 43

Anaphylotoxin: Activate basophils and mast cells to degranulate -> inc vascular permeability and contraction of smooth muscle cells -> anaphylaxis

Question 44

What is the function of C3b?

Answer 44

Opsonin: promotes phagocytosis by binding to complement receptors -> activation of phagocytic cells

Question 45

What is the function of C4a?

Answer 45

Anaphylotoxin: weaker than C3a

Question 46

What is the function of C4b:

Answer 46

Opsonin: promotes phagocytosis by binding complement receptor

Question 47

What are the ligand for complement receptor CR1 (CD35)?

Answer 47

C3b > iC3b | C4b

Question 48

Where is compliment receptor CR1 (CD35) distributed?

Answer 48

B-cells Phagocytes RBC Follicular dendritic cells

Question 49

What are the ligands for CR2 (CD21)?

Answer 49

iC3b | C3dg

Question 50

Where is CD2 (CDdg) found?

Answer 50

B cells and epithelial cells

Question 51

What are the ligands for Cr3 (CD18/11b)?

Answer 51

iC3b Zymosan ICAM-1

Question 52

Where is CR3 (CD18/11b) found?

Answer 52

Phagocytes NK cells Follicular dendritic cells

Question 53

What are the ligands for CR4 (CD18/11c)?

Answer 53

iC3b

Question 54

Where is CR4 found?

Answer 54

Phagocytes

Question 55

What does C5a and b do?

Answer 55

C5b initiates assembly of the MAC | C5a stimulates inflammation

Question 56

What are the three compliment pathways?

Answer 56

Classical, lectin, alternative

Question 57

Where to all the compliment pathways lead?

Answer 57

To the formation of the membrane attack complex

Question 58

What are three mechanism of humoral immune evasion?

Answer 58

Antigenic variation Inhibition of complement activation Resistance to phagocytosis

Question 59

If there is a defective FasL on a T-cell what syndrome does it cause?

Answer 59

Lymphoproliferative syndrome

Question 60

IL4 stimulates IL4R to do ___ while CD40L stimulates CD40 to ___.

Answer 60

Enter mitosis | Class switch

Question 61

What organisms are splenectomy patients vulnerable to?

Answer 61

Encapsulated organisms because you need marginal zone B cells to react but these reside in the white pulp of spleens. Thus these pts have normal reactions to protein antigens but not the lipids and polysaccharides so vaccinate these pts against organisms like S. pneumo

Question 62

What is the cause of Hyper IgM syndrome?

Answer 62

if T cells do not express the CD40L when activating B cells then no class switching is induced so then pt is only able to produce IgM when mounting an immune response Leaves pt susceptible to repeated chronic infections

Question 63

What are the three types of evasion from the humoral system?

Answer 63

Antigenic variation Inhibition of complement activation Resistance to phagocytosis