ABSTRACT
Cytokines, soluble extracellular proteins or glycoproteins, involved in the development and regulation of immune responses have been known to exist since the 1960s. They were thought to be promising agents for therapy of tumors and other diseases, and were initially prepared in vitro or from serum, although the quantities available were too small to do definitive clinical trials. When cytokines became readily available, through recombinant gene technology, they were tested in a variety of diseases with disappointing results. Nonetheless, several cytokines have been approved for therapy and many others are still being studied as promising candidates for immunotherapy.
