ANTIBODIES

def - protein molecules that combine specifically with

antigens. Proteins with antibody activity are known as

immunoglobins.

A. Structure - four polypeptide chains

Fab

Fc- fragment crystalline

light chainheavy chain

SS SS SS

Fragmentantigen binding

DISULFIDE BRIDGES

B. Classes - IgG, IgA, IgM, IgD, IgE

1. IgG

most versatile neutralizes toxins activates complement opsonization - “candy coats” only class to pass the placental barrier longest half life important to secondary response

2. IgM

can form a ringed pentamer only class synthesized in the fetus reacts to ABO blood system excellent at complement fixation excellent at agglutination important in the primary response

3. IgA

antiviral present in tears, saliva, colostrum, sweat,

mucus

4. IgD

found on B cells play a role in B cell differentiation

(formation of plasma cells, which secrete antibody and memory cells which are important to secondary response)

5. IgE

protects against parasitic worms binds to mast cells and basophils play a role in hypersensitivity

C. GENETIC BASIS FOR ANTIBODY FORMATION

1. There are an estimated 1,000,000 to 100,000,000 different Ab in an individual

2. Antibodies are pieced together from distinct regions of DNA

3. Antibody genes can move and rearrange themselves within the genome of a differentiating cell

4. See pages 106-110 AND 121-124 of the notes for more detail