ACE2 and COVID-19: Consistently, the ACE2 peptides detected in the sera of Cohort #4 COVID‐19 patients also contained ACE2 transmembrane domain and cytoplasmic tail (29 of 97 peptides; Appendix Table S1), supporting that the detected ACE2 peptides are derived from exosomal ACE2 proteins rather than soluble ACE2 proteins co‐precipitated with serum exosomes.