Immunoglobulins

Question 1

IgM

Answer 1

Monomeric IgM on naive B Cells - functions as receptor
Free pentameric IgM in circulation
Effector
-Agglutination
-Neutralization
-Complement activation (1 required)
Low affinity, high avidity
1st antibody secreted during the primary immune response

Question 2

IgA

Answer 2

Found primarily in secretions
Most produced antibody in the body (but not much found in serum)
Dimeric or trimeric (mostly dimeric) linked by J-chain
Secretory component added in epithelial cells before secretion
-Increases half-life and stability in harsh environments
Transferred from mother to infants through colostrum and breast milk

Question 3

IgG

Answer 3

Monomeric antibody found in serum circulation
Produced late in primary immune response
Major Ab in the secondary immune response
25% moves between tissues/circulation
21 day half life
Can activate complement (2 are required)
Can be transferred mother to child via passive immunity in placental blood

Question 4

IgE

Answer 4

Very rare and very short half-life in blood
Found bound to high-affinity receptors on mast cells/basophils
Important in defense against helminthic parasites
Associated with allergies/asthma+anaphylactic responses

Question 5

IgD

Answer 5

Synthesized as a membrane-bound receptor for B-cells
Found as a BCR on mature naive B-cells
Free IgD found at low levels in blood
Good marker to target

Question 6

Paratope

Answer 6

Antibody pocket/groove that binds the 3D structures of the epitope

Question 7

B-cell antigenic epitopes

Answer 7

Most important part is 3D-structure, not content

Allows BCR to recognize wide variety of threats

Question 8

Linear epitope

Answer 8

Epitope region is continuous

Question 9

Discontinued epitope

Answer 9

Epitopes regions are not continuous

Denaturation results in loss of binding

Question 10

Antibody binding

Answer 10

Non-covalent bonds between antigen/antibody

Antibodies can bind more than one epitope on multimeric antigens

Question 11

Affinity

Answer 11

Strength at which antibody binds antigen

IgG has higher affinity

Question 12

Avidity

Answer 12

Strength at which a multivalent antibody binds antigen
IgM has more binding sites
Sum of bonds creates overall strong bond

Question 13

Haptens

Answer 13

Antigens that are not immunogenic
Unable to generate an immune response due to lack of cross-linking at BCR
Require carrier protein bound to promote cross-linking