When we get the flu, we feel miserable. We swallow pain relievers, drink lots of tea, slurp down chicken soup. None of these treatments actually eradicates the flu virus itself; our immune system eventually takes care of that. Instead, these remedies make us feel better by alleviating the symptoms: inflammation, dehydration, and congestion. “Most of what makes us sick is actually inflammation—the immune response—not the pathogen itself,” said Ruslan Medzhitov, an immunologist at Yale University.
Yet while scientists have carefully chronicled the damage that the immune system can wreak on the body, they have paid much less attention to the mechanisms in place to repair it. “We spend a lot of our time figuring out how to stop the disease, but the real problem is how to get better, how to recover,” said David Schneider, an immunologist at Stanford University. “It’s possible that getting better is a different thing, not just the reverse of getting sick.”
Schneider and others have begun to study the recovery process on its own, arguing that it is just as essential a component of the immune system as the body’s attempts to eradicate foreign pathogens. They have divided the immune response into two basic categories: the traditional part, dubbed resistance, which fights the pathogen itself; and the less-studied part, called tolerance, which aims to curb or repair the damage inflicted by the pathogen or by resistance mechanisms. The research that they have published in the last few years hints that tolerance may be a crucial factor in whether individuals will survive infections such as malaria, cholera, and sepsis.