Antibody Function

Question 1

What is an epitope or antigenic determinant?

Answer 1

the part of a protein antigen that actually binds specifically to an antibody

Question 2

basic structure of antibody

Answer 2

2 light and 2 heavy chains that are bilaterally symmetrical

can bind 2 identical epitopes (divalent)

Question 3

1) multivalent antigens

2) importance for complex

Answer 3

1) antigens with more than one epitope
(can bind with more than one antibody)
2) immune complex forms because multivalent antigen binds many antibodies, and divalent antibodies can cross-link two antigens

Question 4

Precipitation vs Agglutination

Answer 4

Both are immune complexes

1) Precipitation: when antigen is a molecule
2) Agglutination: when antigen is cell or cell-sized

Question 5

Best antigen to antibody ratio for precipitation

Answer 5

1:1

Question 6

IgM

Answer 6

~ 1st antibody seen in blood
~ great capacity to activate complement since it is decavalent (2 adjacent Fcs needed to activate complement cascade, IgM has 5)
~ viscous b/c of size, makes blood thicker
~ no IgM receptors on phagocytes
~ only antibody to be made by fetus

Question 7

IgG

Answer 7

~ most abundant in blood
~ half-life = 3 wks
~ need 2 IgG’s close together to activate complement
~ opsonizing (phagocytic cells have receptors of Fc of IgG)
~ only antibody that passes from mother to fetus through placenta

Question 8

IgA

Answer 8

~ made by plasma cells in lymphoid tissue near mucous membranes
~ secretory component protects from digestion in gut
~ dimer

Question 9

IgD

Answer 9

~ B cell receptor

Question 10

IgE

Answer 10

~ Fc binds to mast cells and basophils, triggers histamine release
~ causes immediate hypersensitivity (allergies)
~ needed for resistance to parasites (releases release of eosinophil chemotactic factor)