TMPRSS2 and COVID-19: The discrepancy with our current findings, which did not identify an association of genetically predicted BMI or smoking with lung ACE2 and TMPRSS2 expression or with circulating plasma levels of ACE2 may be explained by effects of these risk factors on susceptibility to severe COVID-19 through mechanisms unrelated to lung ACE2 or TMPRSS2 gene expression or plasma ACE2 protein expression.