LGALS9 and COVID-19: Bozorgmehr et al. (2021) demonstrated highly significant positive correlations of plasma Gal-9 levels with a wide range of pro-inflammatory biomarkers in COVID-19 patients. They further demonstrated that Gal-9 treatment of monocytes in vitro enhanced the expression and production of key pro-inflammatory molecules associated with severe COVID-19 disease (Bozorgmehr et al., 2021). Gal-9 induces the secretion of inflammatory cytokines in several immune cell lineages, including monocyte-derived macrophages and neutrophils (Nobumoto et al., 2009; Querol Cano et al., 2019).