A rare cell type in the lungs is essential to survival from the COVID-19 virus, a new study shows.

Experiments in mice infected with the SARS-CoV-2 virus revealed that the immune cell class in question, called nerve and airway-associated interstitial macrophages, or NAMs, may keep the human immune system’s initial counterattack on the virus (lung inflammation) from spiraling out of control to endanger patients.

Macrophages are known to be the first responders to infection, as large immune cells capable of devouring invading viruses and the cells they infect.