Immunotherapy is defined as the use of the immune system or components of it, such as key immune molecules, to fight diseases or invading infectious agents. Modern biotechnology provides industrial versions of immune molecules (components of the immune system) naturally produced by the human body. Immune molecules such as monoclonal antibodies are used as therapeutics in several disease conditions. In recent years a new group of antibody based molecules has been developed to replace monoclonal antibodies, given their ability to overcome some of the limitations of the latter. The first clinical trials with these new molecules have been very encouraging and the promise is that they will be released to the market very soon. This in turn has stimulated more research on new versions of antibody based therapeutics by biotechnological companies supported by the pharmaceutical industry and in many cases in collaboration with academic institutions.