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.