THE IMMUNE SYSTEM AND IGA DEFICIENCY - THE FUNCTION OF IGA IN THE BODYImmunoglobulin A, or IgA, is an antibody produced in the mucous membranes and plays a important role in mucosal immunity. In the mucous membranes, more IgA is produced than all other types of antibodies combined. The amount of IgA produced contributes greatly to the total immunoglobulin production and approximately three to five grams of IgA are secreted into the intestinal lumen each day. IgA is divided into two subclasses, IgA 1 and IgA 2, and can also exist in a dimeric form called secretory IgA, sIgA. IgA1 is the predominant subclass present in serum. Most lymphoid tissues have a predominance of IgA-producing cells. The share of IgA2 production is greater in secretory lymphoid tissues than in non-secretory lymphoid organs (spleen, peripheral lymph nodes, etc.). In IgA2, the heavy and light chains are linked by noncovalent bonds rather than disulfide. The secretory form of IgA, sIgA, is the main immunoglobulin present in mucous secretions such as colostrum and secretions of the genitourinary tract, gastrointestinal tract, prostate. and respiratory epithelium, tears, and saliva (which is important when testing IgA levels for IgA deficiency which will be discussed later in this article) as well as in small amounts of blood. The secretory component of sIgA protects the immunoglobulin from degradation by certain enzymes and allows sIgA to survive in the harsh environment of the gastrointestinal tract and thus provides protection against microbes that multiply in body secretions. Secretory IgA can also inhibit the inflammatory effects of other immunoglobulins (National Library of Medicine, 2011). As noted above, IgA plays a critical role...... middle of article...... Patient and Family Handbook for Primary Immunodeficiency Diseases - Selective IgA Deficiency. 5th ed. Maryland, United States. Izenberg, Neil MD. 2011. Children's health, immune system. [ONLINE] Available at: http://kidshealth.org/parent/general/body_basics/immune.html#. [Accessed 4 Mar 14].Jeffry Modell Foundation, Primary Immunodeficiency Resource Center. 2013. Primary immunodeficiency diseases - Selective IgA deficiency. [ONLINE] Available at: http://kidshealth.org/parent/general/body_basics/immune.html#. [Accessed March 2, 14]. National Library of Medicine - Medical Subject Headings. 2011. Immunoglobulin A. [ONLINE] Available at: http://www.nlm.nih.gov/cgi/mesh/2011/MB_cgi?mode=&term=Immunoglobulin+A. [Accessed April 24, 2014].Worldbook. 2014. Fibroblast research. [ONLINE] Available at: http://worldbookonline.com/advanced/dict?lu=fibroblast. [Accessed April 26 14].