Low α-Thrombin/GPIbα Interaction Is a Potential Contributor to Platelet Hyper-reactivity in COVID-19 Patients

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  Fig. 1. ( A ) GPIbα positively regulates human platelet degranulation induced by low doses of α-thrombin in COVID-19 patients. (Ai) Platelet P-selectin expression was measured (percent of CD62P positive platelets) in washed human platelets by flow cytometry at baseline in 10 healthy donors and 10 COVID-19 patients. Platelets were pretreated with human anti-GPIbα antibody (SZ2, 20 µg/mL) or its isotype IgG control for 5 minutes at 37°C. Degranulation was then initiated by α-thrombin at 0, 0.05 (priming dose), and 0.2 U/mL (positive control). Histogram represents the mean of data ± standard deviation (SD) of plots for P-selectin (CD62P) expression ( n = 10); ** p < 0.01; **** p < 0.0001. Statistical significance was analyzed using one-way analysis of variance (ANOVA) with subsequent Dunnett's t -test for comparison against a single group. (Aii) Effect of anti-GPIbα on P-selectin (CD62P) expression in COVID-19 patients, as assessed by flow cytometry. Left plots represent resting platelets. Right plots represent platelets in the presence of a priming concentration of α-thrombin (0.05 U/mL). (Aiii) ATP release was measured by a Lumi-Aggregometer (Luciferase assay; Chrono-Lume, Chrono-log).…