Scientists have deciphered a key molecular circuit that enables the body to distinguish viruses from bacteria and other microbes, providing a deep view of how dendritic cells cells in mammals fend off different pathogens.

They found a dendritic cell circuit with two major arms: an inflammatory arm, which is highly active during bacterial infections and can initiate a system-wide immune response; and an anti-viral arm, which is induced upon viral infections and coordinates a more focused response tailored to viruses.

A complete understanding of the regulatory network that controls immune responses can help lay the groundwork for more precise interventions, including drugs and vaccines, and could enhance researchers’ understanding of the genetic susceptibilities to infections and other immune disorders.