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CMBM exam 3 > Humoral Immunity > Flashcards

Humoral Immunity Flashcards

1
Q

Which immunoglobulin isotypes can cross the placenta?

A

IgG

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2
Q

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

A

C5b

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3
Q

What are the polypeptide chains that make an antibody?

A

2 identical heavy chains

2 identical light chains

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4
Q

What chromosome are the heavy chain genes on?

A

14

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5
Q

What chromosome are the light chain genes on?

A

2 (kappa) and 22 (lambda)

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6
Q

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

A

Immunologlobulins

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7
Q

Which comes first; the Ig heavy or light chain?

A

The heavy chain comes first

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8
Q

What are the protective mechanisms of binding antibodies to anitgens?

A 
Agglutination
Opsonization
Neutralization
Activation of complement 
Inflammation
Antibody-dependent cell-mediated cytotoxicity
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9
Q

What does agglutination do?

A

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

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10
Q

What does neutralization do?

A

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

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11
Q

What are the characteristics of follicular B cells??

A

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

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12
Q

What are the characteristics of marginal zone B cells?

A

T-independent (IgM); short lived plasma cells

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13
Q

What are the characteristics of B-1 B cells?

A

T-independent (IgM); short lived plasma cells

CD5 positive

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14
Q

What are T-independent antigens?

A

Polysaccharides, nucleic acids, lipids

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15
Q

What are T-dependent antigens?

A

Protein antigens

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16
Q

What are the secondary immune organs?

A

The lymph nodes and the spleen

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17
Q

What is somatic hypermutation (SHM)?

A

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)

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18
Q

What is class switching?

A 
Process by which an Ig changes class or isotype 
The antigenecity is preserved
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19
Q

Where does class switches occur?

A

On the heavy chain

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20
Q

When does class switching occur and what happens during it?

A

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

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21
Q

What are some of the factors in immunoglobulin diversity?

A 
V(D)J recombination
Somatic hypermutation
Class switching
RAG1/RAG2
Base excision and repair
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22
Q

What is hyper IgM syndrome?

A 
Results from mutations affecting class switching which is rare
Decreases the IgG, IgA, IgE
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23
Q

How do you treat hyper IgM syndrome?

A

IVIG, BMT

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24
Q

Describe to me IgM;

A

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

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25
Q

Where is IgM present in the mother?

A

In colostrum (momma milk) to protect newly born

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26
Q

Is IgM produced in secondary immune response?

A

Sometimes

27
Q

Tell me about IgG;

A

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

28
Q

Which Igs fix complements;

A

IgM, IgG

29
Q

Explain the IgA;

A

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

30
Q

Where is IgA present in the mom?

A

Colostrum and momma milk

31
Q

What about IgE?

A

Least common serum Ig which binds to basophils and mast cells

32
Q

What is IgE active in?

A 
Allergic and hypersensitivity rxns
Parasitic infection (helminths) and binds to Fc receptors on eosinophils
33
Q

Tell me about those IgD;

A

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

34
Q

What does IgD do biologically?

A

Who knows

35
Q

Describe IgA1;

A

Monomeric and found in the blood and extracellular spaces

36
Q

Describe IgA2;

A

Dimeric and found in mucous and secretions

37
Q

What are the characteristics of the primary antibody response?

A

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

38
Q

What are the characteristics of the second antibody response?

A

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

39
Q

What is the process of opsonization and phagocytosis?

A

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

40
Q

What is the process of compliment-mediated cytolysis?

A

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

41
Q

What is the process of stimulation of inflammatory reactions?

A

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

42
Q

What is the function of C2b?

A

Prokinin: Cleaved by plasmin -> Kinin -> Edema

43
Q

What is the function of C3a?

A

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

44
Q

What is the function of C3b?

A

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

45
Q

What is the function of C4a?

A

Anaphylotoxin: weaker than C3a

46
Q

What is the function of C4b:

A

Opsonin: promotes phagocytosis by binding complement receptor

47
Q

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

A

C3b > iC3b

C4b

48
Q

Where is compliment receptor CR1 (CD35) distributed?

A

B-cells
Phagocytes
RBC
Follicular dendritic cells

49
Q

What are the ligands for CR2 (CD21)?

A

iC3b

C3dg

50
Q

Where is CD2 (CDdg) found?

A

B cells and epithelial cells

51
Q

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

A

iC3b
Zymosan
ICAM-1

52
Q

Where is CR3 (CD18/11b) found?

A

Phagocytes
NK cells
Follicular dendritic cells

53
Q

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

A

iC3b

54
Q

Where is CR4 found?

A

Phagocytes

55
Q

What does C5a and b do?

A

C5b initiates assembly of the MAC

C5a stimulates inflammation

56
Q

What are the three compliment pathways?

A

Classical, lectin, alternative

57
Q

Where to all the compliment pathways lead?

A

To the formation of the membrane attack complex

58
Q

What are three mechanism of humoral immune evasion?

A

Antigenic variation
Inhibition of complement activation
Resistance to phagocytosis

59
Q

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

A

Lymphoproliferative syndrome

60
Q

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

A

Enter mitosis

Class switch

61
Q

What organisms are splenectomy patients vulnerable to?

A

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

62
Q

What is the cause of Hyper IgM syndrome?

A

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

63
Q

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

A

Antigenic variation
Inhibition of complement activation
Resistance to phagocytosis

CMBM exam 3 (24 decks)

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