Immunoglobulin A plays a role in mucosal immunity and is produced in mucosal linings. Hence IgA can be found in mucous secretions, including tears, saliva, colostrum, secretions from the gastrointestinal tract, and others, but it is found only in small amounts in blood.
The amount of IgA produced in is greater than all other types of antibody combined. 15% of total immunoglobulins produced throughout the body are IgAs, which accounts for about 4 grams each day.
There are two isotypes, (90%) and (10%), They are both heavily glycosylated proteins with IgA1 being found in serum and produced in bone marrow B cells, and , being secreted into colostrum, maternal milk, tears and saliva. IgA can exist as a monomer or in a dimeric form called secretory IgA (sIgA).
Secretory IgA (sigA)
The secretory IgA consists of polymers of two IgA monomers linked by additional so-called J-chains and a secretory component that is wrapped around the IgA dimer in order to protect it from proteolytic digestion in the intestinal tract.
Some bacteria release a protease that destroys IgA which can be utilized in biotechnological experiments.
These include Neisseria gonorrhoeae, Streptococcus pneumoniae, and Haemophilus influenzae type B.
Selection of anti-IgA secondary antibodies
Links to other secondary antibody-types