A tiny invader, perhaps a virus or a microbe, enters the body, and our ancient immune system responds. But how does it know what kind of invader has landed? And once it knows, how does it decide what kind of immune response it should launch?
In humans, the immune system consists of two parallel systems working with one another to fend off invaders. One is the innate immune system, the other the adaptive immune system.
Immunologist Bali Pulendran studies how those two systems work together to identify and respond to all kinds of intruders including pathogens, viruses and microbes.
It’s the innate immune system’s job to recognize the first signs of infection—that is, the moment a pathogen enters the body. “In a sense they act as smoke detectors if you will,†says Pulendran. “Little alarms.â€