Immunoglobulin A

Immunoglobulin A ( IgA) is an antibody (eg Urogenitalschleim, milk, or intestines fluids) occurs mainly in the external body fluids, where it forms a major defense barrier against pathogens. In the serum, it constitutes about 15% of all immunoglobulins. It is synthesized by plasma cells below the epithelium. IgA may occur or as a dimer (two molecules bound at the long ends of the antibody -Wye ) as monomer ( only one molecule that is ). When the dimers are the so-called secretory IgA ( sIgA ).

Structure

There are two subclasses, IgA1 and IgA2. These differ in the molecular mass of the H chain ( IgA1: 56 kDa, IgA2: 52 kDa, the total molecular mass of 160 kDa but in both ) and in the serum concentration ( IgA1: 3 mg / ml, IgA2: 0.5 mg / ml).

SIgA a whole consists of two IgA molecules, a so-called J- chain and a polypeptide having a molecular mass of 70 kDa, the so-called secretory component, or Sekretionsstück (SC- chain). SC - chain is required for transport to mucous membranes and as a protection against digestive enzymes. This polymerization takes place only in the mucous membranes, since it is necessary for the transport across the epithelial cells.