A proprietary preparation of natural human interferon alpha (IFN alpha) with potential immunomodulatory and antineoplastic activities. Natural human interferon alpha OPC-18 binds to cell-surface IFN alpha receptors (IFNARs), resulting in the transcription and translation of genes whose products mediate antiviral, antiproliferative, and immune-modulating effects. IFN alpha is a type I interferon produced by peripheral blood leukocytes or lymphoblastoid cells when exposed to live or inactivated virus, double-stranded RNA, or bacterial products and is the primary interferon produced by virus-induced leukocyte cultures. In addition to its pronounced antiviral activity, it activates NK cells.