Secretory IgA (sIgA) consists of two IgA monomers joined by the J-chain and a secretory component.  It is secreted in plasma cells based in the lamina propia of mucosal membranes. Synthesis of sIgA is independent from the synthesis of serum IgA. This means a lack of serum IgA does not necessarily mean a lack of sIgA. Secretory IgA is the major immunoglobulin in saliva, tears, colostrum, nasal mucus, mother´s milk, tracheobronchial, and gastrointestinal secretes. It plays a major role in preventing adherence of microorganisms to mucosal sites, in activation of the alternative complement pathway, and in activating inflammatory reactions. Newborns are provided with sIgA through their mother´s milk and are passively immunized against gastrointestinal infections.