Introduction
Human Immunoglobulin A (IgA) is the most abundant antibody isotype in mucosal secretions and exists in two subclasses IgA-1 and IgA-2 (1). While circulating serum IgA-1 occurs mainly in the monomeric 160 kDa form (2), mucosal secretary IgA-2 is in dimeric form and serves as the first line of defense against microorganisms through immune exclusion (3). Selective IgA deficiency is the most common primary immunodeficiency observed by a maturation defect in B cells to produce IgA (4). IgA nephropathy is the primary glomerulonephritis characterized by IgA deposition in the kidney and associated with a dysregulation of the immune response (5-6).

Principle of the Assay
The AssayMax Human IgA ELISA (Enzyme-Linked Immunosorbent Assay) kit is designed for detection of human IgA in plasma, serum, urine, saliva, milk, and cell culture supernatants. This assay employs a quantitative sandwich enzyme immunoassay technique that measures human IgA in less than 4 hours. A polyclonal antibody specific for human IgA has been pre-coated onto a 96-well microplate with removable strips. IgA in standards and samples is sandwiched by the immobilized antibody and the biotinylated polyclonal antibody specific for IgA, which is recognized by a streptavidin-peroxidase conjugate. All unbound material is then washed away and a peroxidase enzyme substrate is added. The color development is stopped and the intensity of the color is measured.