[W6] Antibodies: biological affector functions

Question 1

How many antibody specificities can one person produce?

Answer 1

Around 10⁸

Question 2

What explains antibody diversity despite limited gene number?

Answer 2

Gene segment recombination, junctional diversity, and somatic hypermutation

Question 3

How many gene segments encode light and heavy chains?

Answer 3

Light: 3 (V, J, C); Heavy: 4 (V, D, J, C)

Question 4

What are the five classes of antibodies?

Answer 4

IgM, IgG, IgA, IgE, IgD

Question 5

What are the two types of light chains?

Answer 5

Kappa (κ) and Lambda (λ)

Question 6

What determines antibody isotype?

Answer 6

The constant region of the heavy chain

Question 7

What is class switching in B cells?

Answer 7

The process by which a B cell changes its antibody isotype while keeping the same antigen specificity

Question 8

Why is class switching important?

Answer 8

It allows antibodies to function in different biological contexts (e.g., mucosal vs systemic)

Question 9

Which isotype is first produced in an immune response?

Answer 9

IgM

Question 10

Which is the most abundant antibody in serum?

Answer 10

IgG

Question 11

Which antibody provides mucosal immunity?

Answer 11

IgA

Question 12

Which antibody is involved in allergies and parasite defense?

Answer 12

IgE

Question 13

What is the main function of IgD?

Answer 13

Functions as a receptor on naive B cells

Question 14

Which antibody dominates the primary response?

Answer 14

IgM

Question 15

Which antibody dominates the secondary response?

Answer 15

IgG

Question 16

Which response is faster and stronger?

Answer 16

Secondary response

Question 17

What is the primary function of antibodies?

Answer 17

Specific antigen binding via the Fab region

Question 18

What are secondary functions of antibodies?

Answer 18

BCR signalling, agglutination, opsonization, neutralization, complement activation, ADCC, mast cell activation, passive immunity

Question 19

What region of the antibody mediates effector functions?

Answer 19

The Fc (constant) region

Question 20

What is agglutination?

Answer 20

Antibody cross-links multiple antigens/pathogens, forming large complexes

Question 21

What is opsonization?

Answer 21

Tagging pathogens for phagocytosis via binding to Fcγ receptors on phagocytes

Question 22

What is neutralization?

Answer 22

Blocking pathogen or toxin binding to host cells

Question 23

What does IgA do at mucosal surfaces?

Answer 23

Blocks microbial adherence and neutralizes pathogens

Question 24

What cells carry out ADCC?

Answer 24

NK cells

Question 25

What receptor do NK cells use to recognize antibody-coated cells?

Answer 25

FcγRIII (CD16)

Question 26

What happens during ADCC?

Answer 26

NK cells release perforin and granzymes, inducing apoptosis in the target

Question 27

What receptor does IgE bind on mast cells?

Answer 27

FcεRI

Question 28

What is released during mast cell degranulation?

Answer 28

Histamine, prostaglandins, leukotrienes, eosinophil chemotactic factor

Question 29

What triggers IgE crosslinking on mast cells?

Answer 29

Binding of allergen to multiple IgE molecules

Question 30

Which antibody crosses the placenta?

Answer 30

IgG

Question 31

Which antibody is transferred through breast milk?

Answer 31

IgA (as secretory IgA)

Question 32

What is the function of passive maternal antibodies?

Answer 32

Protect the neonate from infections during early life

Question 33

How do humans receive maternal antibodies?

Answer 33

Mostly via placenta (IgG), some via milk (IgA)

Question 34

How do cows, sheep, and pigs receive antibodies?

Answer 34

Via milk (colostrum), as no placental transfer occurs

Question 35

How do birds receive maternal antibodies?

Answer 35

IgG is deposited in egg yolk