Lecture 5

Question 1

Basic structure of antibodies

Answer 1

2 heavy chains, 2 light chains bound by disulfide bridges and noncovalent interactions; 2 Fab fragments, 2 Fc fragments

Question 2

Secreted IgG vs. Membrane bound IgM

Answer 2

Heavy chain C regions end in tail pieces on IgG; C-terminal portion has cytoplasmic area that anchors molecule to plasma membrane

Question 3

Proteolysis of IgG by Papain

Answer 3

Cleaves IgG into 2 Fab fragments and an Fc fragment

Question 4

Proteolysis of IgG by Pepsin

Answer 4

Generates single bivalent F(ab’)2 fragment

Question 5

Hinges in Abs

Answer 5

Generate flexibility for binding to different types of Ags

Question 6

Affinity of Antibody

Answer 6

Tightness of Ag-Ab binding; higher binding constant means Ab is less likely to dissociate from Ag

Question 7

Antibody valency

Answer 7

Maximum number of antigenic determinants with which the Ab can react, can increase tightness of binding

Question 8

Avidity

Answer 8

Overall strength of Ab-Ag complex dependent on affinity and valence

Question 9

IgA

Answer 9

Most common in mucosal secretions; has a secretory component and J chain

Question 10

IgM

Answer 10

Mainly found in plasma/blood stream; first Ab produced on B cell; large molecule

Question 11

IgE

Answer 11

Absorbed on surface of mast cells; present at very low levels; involved in acute inflammation, allergic reaction

Question 12

IgG

Answer 12

Most abundant in blood, provides bulk of immunity to bloodborne pathogens - 4 different subclasses

Question 13

IgD

Answer 13

Low quantities in circulation; primary function is Ag receptor on B lymphocytes