A balanced proportion of macrophages and a set of 11 "protection-defining genes" were probably responsible for less severity in some Covid patients compared to others.

The researchers evaluated the impact of Covid on those who were severely ill and those who were not. For the study, researchers created a unique model comprising of a mouse engrafted with human lung tissue and boosted with a human immune system produced from stem cells to monitor the several stages of SARS-CoV-2 infection and Covid-19 disease.

The observation from the study revealed that no viruses were found in the lungs, and with a more diversified macrophage population that includes both regulatory and inflammatory macrophages, one may more effectively regulate the signals driving antiviral responses, turning them off when necessary. A set of 11 genes were found to work harder and were required to be expressed by the macrophages to protect the lung.

The study was published in the Cell Reports. Such studies could help with the development of new drugs that better prepare immune systems to fight the virus.