Directing the immune system with chemical compounds.

Agonists of immune cell receptors direct innate and adaptive immunity. These agonists range in size and complexity from small molecules to large macromolecules. Here, agonists of a class of immune cell receptors known as the Toll-like receptors (TLRs) are highlighted focusing on the distinctive molecular moieties that pertain to receptor binding and activation. How the structure and combined chemical signals translate into a variety of immune responses remain major questions in the field. In this structure-focused review, we outline potential areas where the tools of chemical biology could help decipher the emerging molecular codes that direct immune stimulation.