The biosynthesis of secretory component and its role in the transepithelial transport of IgA dimer.

How animals protect their mucosal surfaces from environmental pathogens has been of much recent interest. Elucidation of the defence mechanisms involved led to the concept of a common mucosal immune system, characterized by an intimate relationship between mucosal epithelia and migrating populations of IgA-producing B cells(1). However, in order to protect mucosal surfaces fom environmental antigens the dimeric IgA antibodies must somehow be transported across the mucous or exocrine gland epithelia and released into the external secretions. In this article R. Solari and J.-P. Kraehenbuhl show how the secretory component may facilitate this movement and also discuss its possible biosynthesis and processing.