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CMBM exam 3 > Humoral Immunity > Flashcards

Flashcards in Humoral Immunity Deck (63):
1

Which immunoglobulin isotypes can cross the placenta?

IgG

2

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

C5b

3

What are the polypeptide chains that make an antibody?

2 identical heavy chains
2 identical light chains

4

What chromosome are the heavy chain genes on?

14

5

What chromosome are the light chain genes on?

2 (kappa) and 22 (lambda)

6

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

Immunologlobulins

7

Which comes first; the Ig heavy or light chain?

The heavy chain comes first

8

What are the protective mechanisms of binding antibodies to anitgens?

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

9

What does agglutination do?

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

10

What does neutralization do?

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

11

What are the characteristics of follicular B cells??

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

12

What are the characteristics of marginal zone B cells?

T-independent (IgM); short lived plasma cells

13

What are the characteristics of B-1 B cells?

T-independent (IgM); short lived plasma cells
CD5 positive

14

What are T-independent antigens?

Polysaccharides, nucleic acids, lipids

15

What are T-dependent antigens?

Protein antigens

16

What are the secondary immune organs?

The lymph nodes and the spleen

17

What is somatic hypermutation (SHM)?

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)

18

What is class switching?

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

19

Where does class switches occur?

On the heavy chain

20

When does class switching occur and what happens during it?

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

21

What are some of the factors in immunoglobulin diversity?

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

22

What is hyper IgM syndrome?

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

23

How do you treat hyper IgM syndrome?

IVIG, BMT

24

Describe to me IgM;

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

25

Where is IgM present in the mother?

In colostrum (momma milk) to protect newly born

26

Is IgM produced in secondary immune response?

Sometimes

27

Tell me about IgG;

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

28

Which Igs fix complements;

IgM, IgG

29

Explain the IgA;

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

30

Where is IgA present in the mom?

Colostrum and momma milk

31

What about IgE?

Least common serum Ig which binds to basophils and mast cells

32

What is IgE active in?

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

33

Tell me about those IgD;

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

34

What does IgD do biologically?

Who knows

35

Describe IgA1;

Monomeric and found in the blood and extracellular spaces

36

Describe IgA2;

Dimeric and found in mucous and secretions

37

What are the characteristics of the primary antibody response?

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

What are the characteristics of the second antibody response?

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

What is the process of opsonization and phagocytosis?

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

40

What is the process of compliment-mediated cytolysis?

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

What is the process of stimulation of inflammatory reactions?

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

What is the function of C2b?

Prokinin: Cleaved by plasmin -> Kinin -> Edema

43

What is the function of C3a?

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

44

What is the function of C3b?

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

45

What is the function of C4a?

Anaphylotoxin: weaker than C3a

46

What is the function of C4b:

Opsonin: promotes phagocytosis by binding complement receptor

47

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

C3b > iC3b
C4b

48

Where is compliment receptor CR1 (CD35) distributed?

B-cells
Phagocytes
RBC
Follicular dendritic cells

49

What are the ligands for CR2 (CD21)?

iC3b
C3dg

50

Where is CD2 (CDdg) found?

B cells and epithelial cells

51

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

iC3b
Zymosan
ICAM-1

52

Where is CR3 (CD18/11b) found?

Phagocytes
NK cells
Follicular dendritic cells

53

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

iC3b

54

Where is CR4 found?

Phagocytes

55

What does C5a and b do?

C5b initiates assembly of the MAC
C5a stimulates inflammation

56

What are the three compliment pathways?

Classical, lectin, alternative

57

Where to all the compliment pathways lead?

To the formation of the membrane attack complex

58

What are three mechanism of humoral immune evasion?

Antigenic variation
Inhibition of complement activation
Resistance to phagocytosis

59

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

Lymphoproliferative syndrome

60

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

Enter mitosis
Class switch

61

What organisms are splenectomy patients vulnerable to?

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

What is the cause of Hyper IgM syndrome?

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

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

Antigenic variation
Inhibition of complement activation
Resistance to phagocytosis