' When a virus invades your cells, it kicks your immune machinery into motion. The first responders are signaling proteins, called interferon. And they trigger downstream immune responses. So you can kind of think of them as the hormones of the immune system. They're triggered and then they stimulate a bunch of other immune responses that are more specific to that pathogen .' Michelle Baker, a comparative immunologist at the Australian Animal Health Laboratory.
Beginning in 35 seconds.