Chapter Four (Part I)

Question 1

What is an antigen?

Answer 1

any molecule of part of a molecule that is specifically recognized by the highly specialized recognition proteins of lymphocytes

Question 2

What are immunoglobulin (Igs)

Answer 2

proteins on B cells produced in a vast range of antigen specifies. each B cell producing immunoglobulins of a single specificity

Question 3

What is a B cell receptor (BCR)?

Answer 3

membrane bound form of immunoglobulin on the B cell surface that serves as the cell’s receptor for antigen

Question 4

What are plasmablasts & plasma cells?

Answer 4

terminally differentiated B cell that secrete form of immunoglobulin of the same antigen specificity (only one kind)

Question 5

What is the main effector function of B cells in adaptive immunity?

Answer 5

secretion of antibodies which bind pathogens or their toxic products in the extracellular spaces of the body

Question 6

What are the 2 functions of antibodies?

Answer 6

1. specifically bind to antigen (BINDING) 2. engage the elimination mechanisms - recruit other cells and molecules to destroy the pathogen (CLEARANCE)

Question 7

What is the variable region?

Answer 7

on the antigen binding region varies extensively between antibody molecules

Question 8

What is the constant region?

Answer 8

engage the effector functions & does not vary

Question 9

What are the 5 classes of immunoglobulins?

Answer 9

1. IgM 2. IgD 3. IgG 4. IgA 5. IgE

Question 10

How many polypeptide chains in IgG?

Answer 10

4: 2 heavy (50kDa x 2) + 2 light (25kDa x 2)

Question 11

What is true about the molecular weight of IgG?

Answer 11

large molecules: approx 150kDa

Question 12

What are the 2 kinds of light chains found in antibodies?

Answer 12

lambda and kappa. ratio varies species to species

Question 13

What happens when lambda & kappa light chain ratios are off?

Answer 13

abnormal proliferation of B cell clone bc all progeny of B cell will express the same light chain

Question 14

What heavy chains correspond to IgM, IgD, IgG, IgA, & IgE?

Answer 14

μ, δ, γ, α, and ε

Question 15

What is the most abundant immunoglobulin serum?

Answer 15

IgG (several subclasses in humans: Ig1, 2, 3, 4)

Question 16

What is an Ig domain?

Answer 16

compactly folded region of protein: 2 Ig domains in light chain & 4 in heavy chain

Question 17

How many AA in each chain of an Ig?

Answer 17

110 similar but not identical sequences

Question 18

How many B sheets in each V or C domain?

Answer 18

2

Question 19

What are B sheets made of?

Answer 19

B strands

Question 20

What is the main difference between V and C domains?

Answer 20

V domain is larger and contains extra beta strands called C’ and C’’. in V domain flexible loops formed btwn some beta strands contrbute to antigen binding site of Ig molecule

Question 21

Can an antibody by cleaved into functionally distinct fragments?

Answer 21

yes (by pepsin or papain)

Question 22

What allows for flexibility in binding multiple antigens?

Answer 22

hinge region

Question 23

What forms the antigen binding site?

Answer 23

localized regions of hypervariable

Question 24

How do antibodies bind antigens?

Answer 24

via contacts in CDRs that are complementary to the size and shape of antigen

Question 25

What noncovalent forces to antibodies use to bind to antigens?

Answer 25

1. electrostatic forces 2. H bonds 3. Ver der Waal forces 4. hydrophobic forces 5. cation-pi interaction

Question 26

What influences antibody interaction w/ intact antigens?

Answer 26

steric constraints

Question 27

How do antibodies between species differ?

Answer 27

alternative structure (different # of Ig domains)