SELP and COVID-19: Second, reduced aggregation responses are not linked to previous platelet activation in vivo resulting in “exhausted platelets.” The expression of surface P-selectin (Figure 3) and activated GPIIb/IIIa (Figure 4) was negligibly low at the baseline in the patients with COVID-19, with no differences in comparison with that in the patient or healthy controls (P-selectin) or with even significantly lower expression levels compared with that in both the control groups (activated GPIIb/IIIa).