The alternative antigen pathway.

In this article, John Tew, Marie Kosco and Andras Szakal describe progress in deciphering a novel antigen pathway that represents an alternative to classical clearance by phagocytes. Upon booster immunization, immune complexes form rapidly and these complexes are handled not only by phagocytes but also by a series of non-phagocytic cells in a distinct pathway. Ultimately, immunogen in this alternative pathway is delivered to antigen-specific B cells in lymphoid nodules which process and present antigen to T cells. B cells obtain immunogen from follicular dendritic cells in the form of immune complex coated bodies or 'iccosomes'. Antigen-specific B cells appear to find these newly discovered iccosomes especially palatable.