In mono-CD16+ cells in COVID-19 patients, we found reduced lysine degradation (downregulation of NSD1, KMT2E, and SETD2) and enhanced OXPHOS, which may inhibit M2 macrophage polarization and differentiation through the cAMP and MAPK signaling pathways or the PI3K, AKT and mTOR signaling pathways (40, 41). Here, KMT2E is linked to COVID-19.