Type I interferons, constituting IFN-alpha and IFN-beta, were initially des
cribed for their ability to interfere with viral replication. IFN-alpha was
the first cytokine to be cloned and used successfully as a therapeutic cyt
okine, although its mechanism of action remained largely elusive. Evidence
gathered over the last few years shed light on the molecular effects of IFN
-alpha, especially its interaction with the cytokine cascade. Recently, the
principle source of IFN-alpha could be identified as the precursor of type
2 dendritic cells, and IFN-alpha has been identified as the cytokine linki
ng innate with adaptive immunity via its interaction with dendritic cells.