ABSTRACT
In 1957 a substance was described (Isaacs and Lindenmann, 1957) that was produced by virusinfected cell cultures and “interfered” with infection by other viruses; it was called interferon (IFN). Over the following decades it was realized that “IFN” comprises a family of related proteins with several additional properties. Starting in the 1960s various “factors” produced primarily by white blood cells (WBC) as well as other cell supernatants were described which acted in various ways on other WBCs or somatic cells. They were usually given a descriptive name either associated with their cell of origin or their activity on other cells resulting in a myriad of names. The application of molecular technology allowed us to determine that some cytokines had multiple activities and that different cytokines had similar overlapping activities. A systematic
classification based on genetic structure and protein characterization has been effective. The interactive networks and cascades of cytokines, IFN, interleukins (IL), growth factors (GF), chemokines (CK), their receptors (r or R) and signaling pathways are highly complex and will be further explored in this chapter.
