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Immunology > Lecture 6- Immunoglobulins > Flashcards

Lecture 6- Immunoglobulins Flashcards

1
Q

Describe the structure of an antibody

A

Y shaped, joined by disulfide bonds, 2 light chains, 2 heavy chains, variable and constant region, FAB and FC region

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2
Q

What two basic amino acid sequences encode the light chain constant region

A

Kappa and lambda

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3
Q

Do B cell antibodies produce both kappa and lamdba

A

Never, just 1

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4
Q

How are B cell lymphomas marked

A

Increase in frequency in 1 type of light chain

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5
Q

FAB

A

Fragment antigen binding site, smaller, readily penetrate deep into tissues, can’t generate immune response but can neutralize

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6
Q

CroFab

A

Only approved antivenin in US

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7
Q

FC

A

Fragment crystallization

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8
Q

Where does proteolytic cleavage by papain occur

A

Above disulfide bond so end up with 2 FAB regions and 1 FC

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9
Q

Where does proteolytic cleavage by pepsin occur

A

Below the disulfide bone so you get 1 FAB region (F’ab)2 and one FC region (pfc’)

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10
Q

How does variation occur in binding sites

A

Heavy and light chain recombinations and how they interact with each other leads to additional specificity

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11
Q

What region of antibody determines class and function

A

Constant region

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12
Q

What are the 5 classes of antibodies

A

IgM, IgD, IgG, IgA, and IgE

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13
Q

What Ig’s are important for neutralization

A

IgG and IgA

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14
Q

What Ig’s are important for opsonization

A

IgG

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15
Q

What Ig’s are important for sensitization for killing by NK cells

A

IgG

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16
Q

What Ig’s have sensitization of mast cells

A

IgE

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17
Q

What Ig’s have sensitization of basophils

A

IgD and IgE

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18
Q

What Ig’s activate complement

A

IgG and IgM (better)

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19
Q

What Ig transport across epithelium

A

IgA

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20
Q

What Ig transports across placenta

A

IgG

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21
Q

What are the two subtle differences in antibody structure

A

Location of disulfide bonds and different carbohydrates linked to the antibody

22
Q

What is IgM

A

1st class of antibodies produced by B cells after activation, secreted as a pentamer so can’t penetrate tissues, J-chain promotes polymerization, binds with C1 to activate complement

23
Q

What is IgG

A

Most abundant class of antibody, found in blood and tissues, interacts with C1 to activate complement, crosses placenta, 20 day half life

24
Q

How does IgG achieve 20 day half life and why is it important

A

IgG is pinocytoses from plasma and binds to FcRN (neonatal receptors) within endosomes. Once bound IgG-FcRN complex directs endosome away from lysosomes, fuses with cell membrane and releasing IgG back into circulation

25
Q

Monomeric IgA

A

Found in blood stream, engage in neutralization, BCR on memory B cells

26
Q

IgA1

A

Activates alternative pathway, mostly found in serum

27
Q

IgA2

A

Does not activate complement, most found in secretions

28
Q

What do both isotypes of IgA do

A

Bind Fc receptors on phagocytic cells- initiate phagocytosis and respiratory burst

29
Q

Secretory IgA

A

Found at mucosal surfaces- secreted across epithelium into breastmilk, tears, saliva, gut and respiratory mucosa
Neutralize antibodies

30
Q

Selective IgA deficiency

A

Loss of IgA production, leads to increased risk of infections at mucosal surfaces

31
Q

IgE

A

Binds with high affinity to mast cells and basophils, important in fighting parasites and allergic reactions- triggers release of histamine and interleukins

32
Q

IgD

A

Signals for B cell activation, enhances mucosal immunity

33
Q

IgY

A

Found in birds, reptiles and lungfish

34
Q

Where is IgM found

A

Blood

35
Q

Where is IgG found

A

Blood, extracellular fluid, tissues

36
Q

where is IgA found

A

Secretions across epithelia like breastmilk

37
Q

Where is IgE found

A

Associated with mast cells so right beneath the skin

38
Q

What are the 6 antibody functions

A
  1. B cell activation
  2. Neutralization
  3. Optimization
  4. Complement activation
  5. Antibody dependent cellular toxicity
  6. Mast cell and basophil activation
39
Q

What is B cell activation

A

BCR bound to CD79A and CD79B, enough binding of BCR’s will activate B cells

T cell independent, doesn’t generate memory cells

40
Q

Neutralization

A

Virus binds to receptor on cell surface and receptor endocarditis virus and it starts releasing viral DNA

To prevent things antibody blocks binding to virus receptor and can also block fusion by binding to virus

41
Q

Opsonization

A

Bacterium is coated with complement and IgG antibody, C3b binds to CR1 and antibody binds to Fc receptor and bacteria are phagocytosed. Macrophage membranes fuse created enclosed vesicle, the phagocyte. Lysosome fuses and degrades bacteria.

42
Q

Fc receptor free antibody vs aggregation of antibodies

A

Free antibody does not cross link Fc receptors, binding to an aggregation of antibodies like those on bacterial surfaces activates the macrophage leading to phagocytosis

43
Q

Complement activation with IgG and IgM

A

Both activate C1 in the classical pathway

44
Q

Why is IgM more efficient in complement than IgG

A

IgM is more efficient because C1 can bind 1 IgM but in IgG it must bind at least 2.

45
Q

Antibody dependent cell mediated cytotoxicity (ADCC)

A

Antibody binds antigen on surface of target cells, FC receptors on NK cells recognize bound antibody, cross linking FC receptors signals NK cell to kill target cell via toxic granules, results in apoptosis

46
Q

Mast cells and basophils

A

Involved in mobilizing cells to site of infection, releasing histamine

Bind IgE and IgG
IgE binds and causes release of cellular contents, increases blood flow and vascular permeability, recruits neutrophils, macrophages, eosinophils, and antigen specific lymphocytes, increases lymph flow

47
Q

What is the main Ig involved in primary immune response

A

IgM

48
Q

What Ig’s are involved in complement activation

A

IgG and IgMw

49
Q

What Ig’s are involved in neutralization

A

IgG, IgA, IgM

50
Q

What Ig’s are involved in opsonization

A

IgG, IgA

51
Q

What Ig’s are involved in ADCC-NK cells

A

IgG

52
Q

What Ig’s are involved in degranulation of mast cells and basophils

A

IgE

Immunology (22 decks)

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