Abstract
Macrophages play a significant part in immunity and immune responses. They assume a defensive role exhibited by their ability to carry on phagocytosis of parasites and microbes. They regulate lymphocyte activation and proliferation and they are essential in the activation process of T- and B-lymphocytes by antigens and allogenic cells. Enhanced bactericidal activity of "activated macrophages" is based on immunologically linked mechanisms involving lymphocytes. Macrophages kill ingested microbes but the mechanism by which this is accomplished is not completely understood. This paper discusses the role of macrophages in relation to immunity.