The killer binds to its target, aims its weapons, and delivers a burst of lethal chemicals. Phagocytes and Granulocytes Phagocytes are large white cells that can engulf and digest foreign invaders. They include monocytes, which circulate in the blood, and macrophages, which are found in tissues throughout the body, as well as neutrophils, cells that circulate in the blood but move into tissues where they are needed. These chemicals, in addition to destroying microorganisms, play a key role in acute inflammatory reactions. Other types of granulocytes are eosinophils and basophils.
Mast cells are granule-containing cells in tissue.
Phagocytes in the Body Specialized phagocytes are found in organs throughout the body. Complement proteins circulate in the blood in an inactive form. Each of the complement proteins performs its specialized job in turn, acting on the molecule next in line. The end product is a cylinder that punctures the cell membrane and, by allowing fluids and molecules to flow in and out, dooms the target cell. Mounting an Immune Response Microbes attempting to get into the body must first get past the skin and mucous membranes, which not only pose a physical barrier but are rich in scavenger cells and IgA antibodies.