immunoglobulin A

Schematic of immunoglobulin A dimer showing H-chain (blue), L-chain (red), J-chain (magenta) and secretory component (yellow). Two views, one rotated 90 degrees with respect to the other, of the amino acid chains comprising secretory IgA1. Colors are: H-chains (blue and light blue), L-chains (red and light red), J-chain (magenta) and the secretory component (yellow). Coordinates of each backbone carbon atom were derived PDB entry 3CHN. Two views, one rotated 90 degrees with respect to the other, of the amino acid chains comprising secretory IgA2. Colors are: H-chains (blue and light blue), L-chains (red and light red), J-chain (magenta) and the secretory component (yellow). Coordinates of each backbone carbon atom were derived PDB entry 3cm9.

Immunoglobulin A (IgA, also referred to as sIgA in its secretory form) is an antibody that plays a role in the immune function of mucous membranes. The amount of IgA produced in association with mucosal membranes is greater than all other types of antibody combined. In absolute terms, between three and five grams are secreted into the intestinal lumen each day. This represents up to 15% of total immunoglobulins produced throughout the body.