CD63 and COVID-19: We also observed significant up-regulation of CD66b, CD177, CD11b, CXCR4, CD147 (the receptor that binds the spike protein of SARS-CoV-2), and CD63 in mature neutrophils from COVID-19 patients compared to healthy controls, as well as significant down-regulation of CXCR2 (Fig. 2G and SI Appendix, Fig. S2A).