Neutrophils are the body’s first line of defense against infection. But if too many attack for too long, they can damage the tissues they’re meant to protect. In the lungs, this damage can lead to acute respiratory distress syndrome, the leading cause of death due to COVID-19. Researchers have found that using a drug to inhibit a protein called PTP1B can prevent lethal lung inflammation in mice. This discovery may lead to better treatments for severe inflammatory conditions like sepsis and COVID-19.