The synthesis of sIgA begins in the plasma cells, which are located in the lamina propria of mucosal tissues. These cells produce dimeric IgA, which is then transported across epithelial cells. This transport is mediated by the polymeric immunoglobulin receptor (pIgR), which binds to the dimeric IgA on the basolateral side of epithelial cells. The complex is then transcytosed to the apical side, where the receptor is cleaved, releasing sIgA into the lumen along with a segment of pIgR known as the secretory component. This secretory component enhances the stability and function of sIgA in harsh mucosal environments.
