We once thought that only our more modern, adaptive immune system had memory. Now a breakthrough in understanding our other, more primitive, immune defences could change how we fight disease
FOR immunologists, the covid-19 pandemic has been a steep learning curve. “We’ve learned much more about the host immune response to SARS-CoV-2 in a matter of a few months than we have about many, many other viruses that we’ve dealt with for decades,” says Bali Pulendran at Stanford University in California. At every turn, the virus has confounded expectations, from why it leaves some people unscathed but kills others in days to the “cytokine storms” that wrack the bodies of those who become seriously ill. And then there was the nail-biting wait to see if vaccines were possible. But one discovery above all will have immunologists rewriting their textbooks.
This concerns a long-neglected backwater of the immune system called innate immunity. Once seen as a rather prosaic and primitive bit of human biology, it now turns out to play a pivotal, and often decisive, role in the body’s reaction to SARS-CoV-2 and the vaccines against the virus. And not just that: a better appreciation of it is also being touted as our best bet for seeing off the next pandemic.
Being vertebrates, we are the proud owners of two immune systems (see “Meet your immune system”). One is the “adaptive” system, a smart and highly effective special force that develops and deploys precision weapons against invaders. This is the now-familiar arsenal of antibodies and T-cells that have been such a focus of interest during the pandemic. It is often what people mean when they talk about “the” immune system. But it is only half of the story.
The other half is the innate immune system, which is …