What is the difference between IgA, IgD, IgE, IgG and IgM?
- IgA - found in mucosal areas such as the gut, respiratory tract, urogenital tract, tears, breastmilk and saliva and prevents colonisation by pathogens.
- IgD - functions mainly as an antigen receptor on B cells that have not been exposed to antigens before. It has been shown to activate basophils and mast cells to produce antimicrobial factors.
- IgE - binds to allergens and triggers histamine release from mast cells and basophils and is involved in allergy. Also protects against parasitic worms.
- IgG - provides the majority of antibody-based immunity against invading pathogens and is the only antibody capable of crossing the placenta to give passive immunity to the fetus.
- IgM - expressed on the surface of B cells (monomer) and in a secreted form (pentamer) with very high avidity. Eliminates pathogens in the early stages of B cell mediated (humoral) immunity before there is sufficient IgG.