Blood serum is blood plasma without clotting factors. Basophils contain anticoagulant heparin , which prevents blood from clotting too quickly. Platelets are important in the clotting of blood. Lupus anticoagulant in living systems cause an increase in inappropriate blood clotting. Phosphatidylserine plays a role in blood coagulation (also known as clotting). Platelets are the cellular component of the blood that is responsible for clotting. Saliva contains tissue factor which promotes the blood clotting mechanism. Anticoagulants are drugs that interfere with the clotting cascade. Fibrinogens are responsible for clotting blood to help prevent blood loss. P2Y receptors mediate responses including vasodilation, blood clotting, and immune response. An enzyme called plasmin inhibits clotting in the menstrual fluid. Concurrent use with other medications that affect blood clotting can further increase this risk. All infected people show some decreased blood clotting. It is associated with narrowing of blood vessels subsequent to clotting. It also increases the risk of yeast infections, headaches, and blood clotting problems.