Serum immunoglobulin A

IgA accounts for 10% to 20% of the total serum immunoglobulins and can be divided into serotypes and secretory types. Secretory IgA is the major immunoglobulin in exocrine fluids such as colostrum, saliva, tears, intestinal secretions, and bronchial secretions. Therefore, it plays an important role in the first line of defense against infection, especially in the respiratory and intestinal tracts, which can be called local immunity.