Granulocytes are white blood cells that contain granules filled with potent chemicals, which allow the granulocytes to destroy microorganisms. Some of these chemicals such as histamine also contribute to inflammation and allergy. Rather, it is found in the lungs, skin, tongue, and linings of the nose and intestinal tract, where it is responsible for the symptoms of allergy. Platelets, too, contain granules. In addition to promoting blood clotting and wound repair, platelets activate some of the immune defenses.
Complement proteins circulate in the blood in an inactive form.
With fluids and molecules flowing in and out, the cell swells and bursts. Mounting an Immune Response Infections are the most common cause of human disease. Microbes attempting to get into the body must first move past the body's external armor. The skin and the membranes lining the body's gateways not only pose a physical barrier, they are also rich in scavenger cells and IgA antibodies. Microbes that cross the nonspecific barriers must then confront specific weapons tailored just for them.