The immune system is the body’s defence mechanism against pathogens. This system comprises of many cells that work together to protect the body from foreign invaders such as bacteria, viruses, parasites as well as tumours. The immune system is divided into two primitive forms, the innate and adaptive systems. The roles for both types are vital in the immune system; the innate is the rapid, non-specific primary response against any foreign material the body encounters, whereas the adaptive system is a secondary response and a more specific line of defence. The adaptive as well as the innate responses initiation are hugely associated with each other. The innate response consists of many components; these include mechanical, chemical, humoral
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Fixed macrophages are found where microbial invasions are likely to occur, thus, providing a rapid response. The differentiated macrophages possess an enhanced cellular protein synthesis as well as secretory mechanism (Takashiba et al. 1991). Also a tissue macrophage is structurally larger than its precursor (monocyte) and can live for several months.
Macrophages play a central role in the immune response, since they are important for both innate and adaptive systems. There are clearly four crucial and distinct functions activated macrophages can perform (Fig.1). Firstly, macrophages are involved in the innate defense inflammatory response by phagocytosing pathogens and excreting several cytokines and chemicals that attract other cells to the injured tissue called “chemotactic factors” as well as supporting the repair of tissue. Secondly, macrophages act as “accessory” cells to initiate the lymphocytes of the adaptive immune response; not only by secreting various cytokines, but also by the presentation of antigens to the T cells in order to recognise them and eliminate the pathogen. Thirdly, macrophages function as effectors in the humoral response by possessing cell surface receptors for immunoglobulin substances and are able to phagocytose antigens that are bound by soluble antibodies.