Platelets from COVID-19 patients express the antiviral protein IFITM3 but not the ACE2 receptor. (A) Integrated Genome Viewer plots demonstrating expression of IFITM3 from the RNA-seq data set. A representative healthy donor and COVID-19 patient are shown. The height of the bars indicates expression level. (B) Immunoblot and densitometric quantification of IFITM3 and β-actin expression in platelets isolated from healthy donors (n = 12) and SARS-CoV-2–infected non-ICU patients (n = 7) and COVID-19 ICU patients (n = 14). (C) RT-PCR analysis of ACE2 was performed on platelets from COVID-19 patients (5 healthy donors and 25 COVID-19 patients). Representative tracing from 2 COVID-19 patients (green and red). HepG2 cells served as a positive control (blue). No reverse transcriptase (RT) served as a negative control (gray). Reactions were performed in triplicate. (D) Immunoblot and densitometric quantification of ACE2 and β-actin expression in platelets isolated from healthy donors and ICU COVID-19 patients (n = 4). Leukocytes (white blood cells [WBC]) served as a positive control. (E) RT-PCR analysis of the SARS-CoV-2 N1 gene in platelets from non-ICU and ICU SARS-CoV-2–infected patients (n = 25). Representative tracing from 1 COVID-19 patient positive for SARS-CoV-2 mRNA presence (red) and 1 patient with SARS-CoV-2 mRNA absence (green). mRNA isolated from tracheal aspirates served as a positive control (blue). No reverse transcriptase served as a negative control (gray). Reactions were performed in triplicate. One PCR band at the correct size was observed in the tracheal aspirates and in the positive platelet samples. The PCR band in the platelet sample was confirmed by Sanger sequencing to be the N1 gene. ***P < .001. ΔRN, fluorescence intensity normalized to baseline.