Final answer:
Heparin, secreted by basophils, acts as an anticoagulant and helps defend the body against infection.
Step-by-step explanation:
Heparin, which is secreted by basophils, helps defend the body against infection by acting as an anticoagulant. It inhibits blood clotting, which is important in preventing the formation of unwanted blood clots that can occur during inflammation or infection. By preventing excessive clotting, heparin allows immune cells and molecules, such as antibodies, to reach the site of infection more easily, aiding in the immune response.