<prompt> The secretory component of immunoglobulin molecule is -Formed by epithelial cells of lining mucosaFormed by plasma cellFormed by epithelial cell and plasma cellSecreted by bone marrow  <response>: The secretory component is a component of immunoglobulin A IgA. Secretory component is a proteolytic cleavage product of the polymeric immunoglobulin receptor which remains associated with dimeric IgA in sero-mucus secretions. Polymeric IgA binds to the polymeric immunoglobulin receptor on the basolateral surface of epithelial cells and is taken up into the cell transcytosis. Ref: Ananthanarayan Panikers textbook of microbiology 9th edition pg:97 