Inflammation and blood clotting seen in very severe cases of Covid-19 may be caused by the antibodies sent to fight the disease activating unnecessary platelet activity in the lungs. A new paper published in the journal Blood reveals how antibodies produced by our bodies to protect against Covid-19 are triggering increased function of platelets, which may be causing fatal blood clots in patients with severe disease. Platelets are small cells found in the blood that form clots to stop or prevent bleeding, but where platelets don't function properly this can lead to serious health concerns such as strokes and heart attacks.