SARS-CoV-2–containing MKs produce NF-κB-mediated cytokines and have a hyperactivated phenotype. (A) Flow cytometry plot of circulating MKs showing expression of NF-κB subunit p65. Quantification of p65 expression in the 3 MK subpopulations (n = 14 donors). (B) Flow cytometry plot of circulating MKs showing expression of NF-κB subunit p52/p100. Quantification of p52/p100 expression in the 3 MK subpopulations (n = 14 donors). (C-E) Histograms and accompanying quantification of PrimeFlow flow cytometry for cytokines in circulating MKs. (C) IL-6 (n = 8 donors), (D) IL-1β (n = 8 donors), and (E) TNF-α (n = 8 donors). (F-J) Percent positive quantification for immunomodulatory proteins from flow cytometry on circulating MKs (n = 14 donors), (F) TLR2, (G) TLR3, (H) TLR4, (I) ICAM1, and (J) HLA-DR. (K-N) Mean fluorescent intensity quantification of (K-L) MK activation markers and (M-N) MK drug targets. (K) P-selectin (n = 20 donors), (L) activated GPIIb/IIIa (n = 11 donors), (M) P2Y12 (n = 82 donors), and (N) PAR-1 (n = 138 donors). Dashed lines in panels K-N represent the geometric mean for the respective isotype control. Percent positive graphs for antibody-based stains in panels A-B,F-J represent percent positive relative to the respective isotype control. All statistical analyses were performed using one-way ANOVA with Tukey post hoc multiple comparisons test. All graphs are given as mean ± SEM. Adjusted P values are ∗P = .05 to .01; ∗∗P = .01 to .001; ∗∗∗P = .001 to .0001; ∗∗∗∗P < .0001. TNF-α, tumor necrosis factor α.