Lecture #6

Question 1

IgA

Answer 1

MOST common Ab in mucosal secretions;

• Major Ig for EXTERNAL SECRETIONS (colostrum, milk, saliva, tears)
• Addition k or lamda L-chains and the H alpha chains
• Secreted contains: 1. Secretory component (SC) 2. J-chain (holds together thru disulfide bridges)

Question 2

IgM

Answer 2

Mainly found in the plasma (large mol weight);

• On B cell
• Has 5 Four-chain basic unit: Two u H-chains and 2 L-chains &laquo_space;held together by disulfide bridges
• Play CRITICAL ROLE in defense before IgG gets there
• Found primarily in bloodstream and provides protection from BLOODBORNE PATHOGENS
• Avidity of an IgM is VERYYYY HIGH, making IgM very effective in removal of microbe

Question 3

IgE

Answer 3

Absorbed on the surface of mast cells;

• Present in SERUM at very low levels
• SIGNIFICANT ROLE in enhancing inflamm, in protection from infection by worms and allergic rxn’s
• Ab-mediated ALLERGY
• receptors on MAST CELLS for Fc (receptor)- once bound then triggers mediators
• Important component of IMMEDIATE HYPERSENSITIVITY SYNDROMES (Such as hay fever and asthma)

Question 4

IgG

Answer 4

Penetrates deeper into the tissue; most BLOODBORNE and TISSUE pathogens

• TWO heavy gamma chains with either TWO k or two lambda light chains
• Different subclasses of IgG (IgG1, IgG2, IgG3, IgG4)

Question 5

Blood IgA

Answer 5

Monomeric structure capable of complement activation

Question 6

IgA on epithelial surfaces

Answer 6

Dimers that can’t activate complement

Question 7

What’s unique about IgG?

Answer 7

Only Ab class to cross the placenta to provide passive humoral immunity to the developing fetus and to the infant on its birth

Question 8

FcRn

Answer 8

Fc Receptor Neonatal- expressed in placenta; transfers the maternal IgG from the maternal to the FETAL CIRCULATION

Question 9

IgD

Answer 9

Present in low quantities;
-PRIMARY FXN: An Ag receptor on B lymphocytes
(Naive B cells express both IgM and IgM)