ABSTRACT
The failure or success of an antibody response directed against an infectious agent depends entirely on their ability to trigger the complement system and/or to induce phagocytosis. Most mammals, including humans, have developed two well-defined systems of phagocytic cells: the polymorphonuclear (PMN) leukocyte system (particularly the neutrophil population) and the monocyte/macrophage system. Both types of cells can engulf microorganisms and cause their intracellular death through a variety of enzymatic systems, but the two-cell systems differ considerably in their biological characteristics.
