Monoclonal Antibodies

Monoclonal Antibodies: Structures and Characteristics

Antibodies(Part 1)

Heavy chains

Heavy chains are approximately 450-550 amino acids in length. Each heavy chain has a constant region which is identical for all antibodies of the same class and a variable region which differs between antibodies.

There are five types of heavy chains g , d , a , m and e . These five types of heavy chains represent the five classes of human immunoglobulins.

The heavy chains form the stem of the “Y”of the monomer.

heavy

IgG IgA IgM IgD IgE

Five classes of antibodies

Class	Heavy Chain	Light Chain	Mg/ml*	Notes
IgG	Gamma (γ)	Kappa or lambda	6-13	Most abundant in blood and tissue liquids. Transfers across placenta. Binds to many types of pathogens.
IgA	Alpha (α)	Kappa or lambda	0.6-3	Major secretory antibody. Secreted across mucosal tract. Found in breast milk, tears and saliva.
IgM	Mu (μ)	Kappa or lambda	0.5-3	“Natural antibody” found in serum without prior contact with antigen. First antibody to appear after immunization.
IgD	Delta (δ)	Kappa or lambda	<0.14	Function not understood.
IgE	Epsilon (ε)	Kappa or lambda	<0.0004	Binds to basophils and mast cells sensitizing them for certain allergic reactions.
				* mg/ml gives the normal concentration in human serum.