PSMB8 and COVID-19: When we constructed a single-cell trajectory for the activation of the immunoproteasome (i.e. expression of PSMB8) in polarized M1 alveolar macrophages, we detected the involvement of lipid catabolic processes and lipid transport in cells from patients with mild COVID-19, but this functionality appeared to be impaired in equivalent cells from patients with severe COVID-19.