Type III interferons: Protective or harmful in COVID-19?

Interferons and other cytokines produced by the immune system are important defenses against viral infections, but as we have seen in COVID-19, they can also contribute to damaging, potentially life-threatening lung inflammation. Recent evidence suggests that one type of interferon, known as type III interferon or interferon lambda (λ), can fight viral infection while limiting this inflammatory damage. That has led to clinical trials to test type III interferon as a treatment for COVID-19.