Immunity is the ability of a body to resist infection or to counter the harmful toxins produced by infecting organisms (Martin, Hine 2008). Antibodies and white blood cells are defensive cells and substances, these things produce an immune response. If such an encounter such as, bacteria, viruses, fungi and parasites occur can make the macrophages engulf the microorganism and secretes cytokines and chemokines. This attracts immune cells to the infected area which are neutrophils and monocytes. These come from nearby blood vessels and this causes the process of inflammation. The system of defensive proteins is also activated. Protein coats the target cells with fragments that can recognize macrophages. The process of the protein is a crucial role because it promotes adaptive or acquired immunity. Adaptive immunity happens throughout a person’s life time and active immunity only comes when the body recognizes there is something wrong such as a virus, infection or immunization. Then there is other immunity and Martin and Hine define this as, “Humoral immunity is when B lymphocytes produce free antibodies that circulate in the bloodstream; cell-mediated immunity is caused by the action of T lymphocytes. Passive immunity is induced by injection of serum taken from an individual already immune to a particular antigen; it can also be acquired by the transfer of maternal antibodies to offspring via the placenta or breast milk. Active immunity tends to be long-lasting; passive immunity is short-lived.
Martin, Elizabeth. Hine, Robert. 2008. Immunity. Oxford University Press. Oxford Reference Online. Oxford University Press. Apollo Group. 27 May 2009