In the new coronavirus (COVID-19), there is a large amount of macrophages in the bronchoalveolar lavage fluid, suggesting that macrophages are greatly involved in the severity. Macrophages are not just phagocytes, they have many subsets, and each has its own functions.
The following group has reported that transcription factors (MAFB and MAF) in macrophages are significantly related to the progression of COVID-19.
https://www.frontiersin.org/articles/10.3389/fimmu.2020.603507/full
MAFB, a transcription factor, promotes a subset of pathogenic pro-fibrotic SPP1+ macrophages, while transcription factor MAF has the function of suppressing inflammatory FCN1+ macrophage subsets. When COVID-19 becomes more severe, the MAFB/MAF ratio increases. In other words, subsets of macrophages are controlled in a direction that accelerates inflammation of lung tissue and simultaneously accelerates fibrosis.
Therefore, they have concluded that it might be effective to silence MAFB and induce overexpression of MAF when treating COVID-19.