Immunoglobulins- Structure, functions and characteristics

IgG, IgA, IgM, IgD, IgE
Y shaped
classified on the basis of heavy chains
Composed of 2 H and 2 L chains
each chain has constant and variables regions
2 fragments- Fab and Fc
cleavage by Papain and pepsin

IgG
Secondary immune response
Opsonizes bacteria
fixes complement
Neutralizes bacterial toxins and viruses
Crosses the placenta

IgA
Prevent attachment of bacteria and viruses to mucous membrane
two types serum IgA and secretory IgA
Present in Saliva, tear, colostrum, milk

IgM
Primary immune response
Fixes complements
Ag receptor on the surface of B cells

IgD
Ag receptor on the surface of B cells

IgE
Mediates immediate hypersensitive
Defends against worm and helminthic infections