Platelets respond to SARS-CoV-2 and modulate monocytes activation in vitro. (A) Platelets, monocytes, and platelet-monocyte cocultures were kept uninfected or exposed to SARS-CoV-2 overnight. (B) The percentage of P-selectin in uninfected and SARS-CoV-2-infected platelets. (C) The fold change in platelet activation markers and mediator secretion after SARS-CoV-2 infection compared with uninfected platelets. (D) The fold change in platelet and monocyte activation markers and mediator secretion after SARS-CoV-2 infection as compared between infected and uninfected monocytes (left), infected and uninfected platelet-monocyte cocultures (middle), or in infected cocultures compared with monocytes infected alone (right). (E) The fold change in platelet activation markers and mediator secretion in SARS-CoV-2 infected cocultures compared with platelets infected alone. (F) Soluble P-selectin (sCD62P) concentration in platelets, monocytes, or platelet-monocyte cocultures after SARS-CoV-2 infection. Bars represent mean ± standard error of the mean of platelets and/or monocytes from 4 independent donors. *P < .05 compared with uninfected platelets or between selected groups.