Lecture 4: Immunoglobulin Structure

Question 1

What do the differences in Ig class represent?

Answer 1

Heavy chain type (mu, gamma, episilon, alpha, delta)

Question 2

What determines the Ig isotype?

Answer 2

H chains (heavy chains)

Question 3

True or false: One immunoglobulin will be kappa or lambda, never both

Answer 3

TRUE - either have 2 lambda or 2 kappa, never one of each

Question 4

What is the Fab region of an antibody?

Answer 4

antigen binding site

Question 5

What is the Fc region?

Answer 5

constant region (heavy chain)

Question 6

What are the 5 classes of antibodies?

Answer 6

G
M
D
A
E

Question 7

What form is IgM found in in the body?

Answer 7

pentameric (can bind to 10 antigens)

Question 8

What form is IgA found in in the blood?

Answer 8

monomeric

Question 9

What form is IgA in mucosal secretions?

Answer 9

dimeric

Question 10

What holds the two IgA monomers together?

Answer 10

J chain

Question 11

Where is the ONLY place IgA is found?

Answer 11

Mucosa

Question 12

Where is the secretory component on the IgA chain?

Answer 12

around the Fc part (hugging the J chain)

Question 13

All immunoglobulins are in the serum except for which one?

Answer 13

IgD (which is on the surface of a B cell)

Question 14

Of the 100mg/mL total protein in blood, what percentage is immunoglobulin?

Answer 14

10

50% albumin

Question 15

What is the half life of antibodies?

Answer 15

3 weeks

Question 16

What is the only immunoglobulin that crosses the placenta?

Answer 16

IgG

Question 17

What is the complement system?

Answer 17

series of enzymatic reactions that happen when antibody binds antigen leading to lysis of cell

Question 18

Crosslinking of ______ on mast cells leads to degranulation

Answer 18

IgE (release of granules leads to histamine release causing allergy)

Question 19

What antibody sits on the surface of mast cells?

Answer 19

IgE

Question 20

When does cross linking on the mast cell occur?

Answer 20

In the presence of an antigen

Question 21

How is the IgE anchored to the mast cell?

Answer 21

Fc receptor

Question 22

What immunoglobulin is responsible for the allergic response?

Answer 22

IgE (contents released from mast cell degranulation lead to response)

Question 23

What are 3 methods mediate humoral immunity?

Answer 23

1) Neutralization (antibody prevents bacterial adherence)
2) Opsonization (antibody promotes phagocytosis)
3) Complement activation (antibody activates complement, which enhances opsonization and lyses some bacteria)

Question 24

What does activation through Fc receptors require?

Answer 24

aggregation of Ig (allows crosslinking of Fc receptors)

Question 25

What does Fc receptor binding do?

Answer 25

activate cells and mobilize them to action (ex: destruction of bacteria by macrophage)

Question 26

When is the critical time for infection in babies in terms of antibody levels?

Answer 26

6-9 months (maternal antibodies plummet and baby is not making much of their own)

Question 27

What antibody does baby make first?

Answer 27

IgM

Question 28

Define monoclonal antibodies

Answer 28

clone of B cells

Question 29

Define polyclonal antibodies

Answer 29

multiple clones of B cells (many different B cells make many different antibodies that recognize multiple epitopes on antigen)

Question 30

What is the predominant Ab induced in primary response?

Answer 30

IgM

Question 31

What is the predominant Ab induced in secondary response?

Answer 31

IgG

Question 32

What Ab is found on the surface of B cells?

Answer 32

IgD

Question 33

Define variable region

Answer 33

combination of variable region of H chain and L chain

Question 34

Which antibody is pentameric in its secreted form?

Answer 34

IgM

Question 35

How do you identify a B cell as such?

Answer 35

Look for monomeric IgM attached

Question 36

Which antibody crosses the placenta?

Answer 36

IgG (due to FcRn on placenta)

Question 37

Which antibody occurs as a dimer?

Answer 37

IgA (but predominantly monomeric in serum)

Question 38

What is the function of antibodies?

Answer 38

bind and neutralize pathogens (facilitate uptake of pathogen by phagocytic cells thru Fc receptor or complement receptors on phagocyte)

Question 39

What cells possess Fc receptors?

Answer 39

phagocytic cells (macs and DCs), NK cells, eosinophils, basophils, mast cells

Question 40

What is the half life for antibody titers?

Answer 40

Tetanus: 11 years Measles: 3014 years

Question 41

When do Ig genes undergo somatic DNA recombination?

Answer 41

During B cell ontogeny

Question 42

Which class of exons are at the 5' end?

Answer 42

V region

Question 43

What follows the V region in the heavy chain? light chain?

Answer 43

Heavy chain: D | Light chain: J