In addition, increased Rab5 expression has been observed in J774E cells (mouse macrophages) treated with the proinflammatory cytokine interleukin-6 (108), in the placentas of severe acute respiratory syndrome 2 (SARS-CoV-2)–positive patients (109, 110), and in cultured cells exposed to particulate matter 2.5 (PM2.5; particles with an aerodynamic diameter <2.5 μm) in combination with SARS-CoV-2 (111). Here, IL6 is linked to severe acute respiratory syndrome.