Immunoglobulin A

Immunoglobulin A (IgA) is an antibody that plays a crucial role in the immune system's function in the 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.

Structure

IgA has two subclasses (IgA1 and IgA2) and can be produced as a monomeric as well as a dimeric form. The IgA dimeric form is the most prevalent and is also called secretory IgA (sIgA).

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Immunoglobulin A

Function

IgA has a key role in preventing infections and controlling the immune response to pathogens. It does this by preventing their access to the body's internal tissues. IgA is also involved in the regulation of microbiota and prevention of autoimmune diseases.

Clinical significance

Abnormalities in IgA levels can lead to health problems. For example, selective IgA deficiency is a relatively common primary immunodeficiency characterized by an inability to produce IgA. People with this condition are more prone to infections, particularly of the mucous membranes in the respiratory tract and gastrointestinal tract.

See also

• Antibody
• Immune system
• Immunoglobulin
• Immunodeficiency