TMPRSS2 and infection: Interestingly, monocyte-derived macrophages have been posited by several papers as a possible mechanism through which the virus may spread beyond the lungs [16,17] and may play a role in hyper-inflammation during infection, but while some studies have shown they may express ACE2 [15,64,65] and TMPRSS2 [66,67], there has been little investigation into whether smoking or vaping affected the expression of these genes in macrophages.