Platelets and Immunity: Going Viral

Platelets are the major blood component bridging immunity and thrombosis. Abundant in the circulation, platelets encounter pathogens at a higher rate than any circulating leukocyte. Viral particles of various blood-borne pathogens such as HIV,1 dengue,2 or even respiratory viruses such as influenza3 are found inside human platelets. Viral infections with these viruses,4 as well as the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), can lead to thrombocytopenia5 along with thrombotic complications6–8 in patients. The presence of internalized viral particles, thrombocytopenia, and thrombosis implicates platelets as active participants in immunity during viral infections