Fig. 4: A proposed scheme for activation of the lectin pathway by dendrimer-IgMB complexes.

G5 dendrimers were chosen as example. Pyrrolidone-terminated dendrimers poorly bind to IgMB and on binding do not induce significant conformational changes in the immunoglobulin structure to promote MBL-MASPs binding. Amine-terminated dendrimers bind to IgM in numbers (and might also promote complex formation with other plasma proteins). This induces conformational changes in IgM and exposes complex oligomannose glycans on the antigen-binding face of the immunoglobulin, thereby allowing MBL binding to complex oligomannose glycans. On MBL binding, MBL activates its MBL-associated serine proteases (MASPs), which, in turn, cleave C4 and C2 to form the lectin pathway C3 convertase.