During ADCC, cells are killed by direct release of toxic proteins, hydrolytic enzymes, and reactive oxygen intermediates onto their membranes. The mediators of antimicrobial and cytotoxic activity of macrophages are listed in table 2-5 . Note that neutrophils use many of the same killing mechanisms as macrophages. Macrophages serve as antigen presenting cells to T helper cells. Macrophages express abundant amounts of MHC class II upon which antigens are displayed for activation of T helper cells.
Macrophages secrete cytokines when activated.
These cytokines trigger inflammation, complement activation, T helper cell activation, call other cells to the site of infection, promote increased hematopoiesis, and induce nearby cells to gear up their intracellular antiviral defenses. Neutrophils, basophils and eosinophils are granulocytes. Their numbers increase greatly during infection due to increased synthesis of them in the bone marrow in response to cytokines. Basophils are present in blood. They contain granules of histamine and other inflammatory mediators.