IgA

 IgA is found as a Monomer in serum but a dimer in secretions and is the dominant class of Antibody found in secretions. These two subclasses differ in susceptibility to bacterial Proteases. IgA has several functions including the inhibition of microbial adherance to mucosal cells and the intestinal protection of neonates as it is present in breast milk. IgA also activates Complement through the alternative pathway.