Interestingly, single-cell analysis of bronchial lavage from COVID-19 patients revealed the presence of monocyte-derived FCN1+ macrophages in severe COVID-19 patients, suggesting a possible role of IL-6 secreted by SARS-CoV-2-infected lung cells in promoting FCN1+ macrophages differentiation from monocytes [37]. Here, FCN1 is linked to COVID-19.