FIGURE 1.

Model of an IgM–NAb complex that enhances interactions between an apoptotic cell and professional phagocytes. In this idealized model, apoptotic death results in membrane alterations that expose a range of neo-determinants. PC-associated membrane determinants are recognized by antigen-binding sites of a pentameric IgM. Binding of PC determinants results in conformational changes in the mu constant regions, which expose a conformational site responsible for recruitment of the globular heads of C1q (Czajkowsky and Shao, 2009). Alternatively, MBL binds to nearby high mannose N-linked glycoconjugates on mu-associated sites (not shown). This polymeric IgM–C1q complex is involved in generating or stabilizing interactions with receptors on professional phagocytes, which enhance apoptotic phagocytosis and blocks inflammatory responses.