Interferon-α1 is a member of the Type I IFN family best known for their antiviral activity. Most nucleated cells　produce one or more Type I IFNs in response to viral infection. Secreted Type I IFN then induces viral protective responses in　neighboring non-infected cells. Type I IFNs also enhance virus-induced apoptosis. Other IFN-α1 activities include　enhancement of dendritic cell maturation and cytotoxic T cell activity. IFN-α1 binds to the IFN-αR1 and IFN-αR2 heterodimer.Intracellular signaling through the Jak/Stat pathway is best characterized. However, the PI3K, ERK, and p38 kinase pathways　are also involved. The antiviral activities of the IFNs have led to their use in treating viral infections. Type I IFNs also appear to　have an integral role in several autoimmune diseases.