Antibody Overview

Porter/Edelman

Porter/Edelman

determined basic Ig structure, nobel prize in 1972

Pepsin Digestion

F(ab’)₂ and Fc fragments

Papain Digestion

Fc, and two Fab fragments

Mercapoethanol Reduction

Two heavy and two light chains

N-terminus

Found in the variable region of the antibody

C-terminus

Found in the constant region of the antibody

Hinge region

Region where Fab and Fc fragments meet, creates “bend” with prolines and cysteines

Disulfide linkages

Stabilize connections between hinge region, C_H1 and C_L

Complementary Determining Region (CDR)

most variable region of light and heavy chains, with CDR3 being the most variable that forms the antigen binding site

kappa and lambda

Light chain constants (3 combinations)

mew, gamma, alpha, delta, or epsilon

Heavy chain constants

Light chain variability

About ½ variable acids

Heavy chain variability

About ¼ variable acids

Carbohydrate side chain

Found on antibody IgA, IgD, and IgG C_H2 domains and IgE and IgM C_H3 domains to facilitate solubility

IgG

most abundant Ab in serum, protects fetus, has hinge region

IgM

produced in primary Ag response, forms a pentamer

IgA

main Ab in secretions (milk, saliva, tears, mucous), has hinge region, forms dimer or tetramer in secretions

IgE

contributes to hypersensitivity by binding to Fc receptors on mast cells and basophils to induce histidine and serotonin

IgD

major membrane Ig along with membrane-bound IgM expressed by mature B-cells, has hinge region

IgG3

contains the longest C-chain of the 4 subclasses of the IgG class

Anti-isotype Antibody

made against foreign Ab C-regions (either heavy or light chains)

mIgM

expressed by immature pre-B cells

mIgM and mIgD

expressed by naive, fully mature unstimulated B-cells