Extract: Dendrimers are hyperbranched synthetic macromolecules that can be made with structural precision. So far, their biomedical applications have been limited to drug delivery. Dendrimers with cationic (i.e., amine or NH3+) end groups are toxic after repeated intravenous use or topical ocular application. In contrast, anionic (i.e., carboxy or COO-) dendrimers are not toxic. For example, cationic dendrimers cause substantial changes to red blood cell morphology at 10 mug/ml whilst anionic dendrimers have no such effect at 2,000 mug/ml. We set out to determine whether the receptor-ligand interactions between carbohydrates and proteins, which mediate many important aspects of cell surface-mediated immuno-regulation could be pharmacologically manipulated using new anionic dendrimer-based drugs. Any such medicine would have to possess multiple and cooperative receptor binding properties. Previous attempts to pharmacologically manipulate such interactions with synthetic linear polymers have failed because of the structural diversity of the polymers used, and because they activated immunological cell death pathways and blood clotting pathways.