Abstract: The interferon are a family of cytokine mediators critically involved in alerting the cellular immune system to viral infection of host cell. Interferon not only exhibit important antiviral effects but also exert a key influence on the quality of the cellular immune response and amplify antigen presentation to specific T cell. Type I interferon (IFN-alpha and IFN-beta) is secreted by virus-infected cell while type II, immune or gamma interferon (IFN-gamma) is mainly secreted by T cell, natural killer (NK) cell and macrophage. Interferon interact with specific cellular receptors, which promote production of second messengers ultimately leading to expression of antiviral and immune modulatory genes. The IFN genes themselves are regulated by transcriptional and posttranscriptional mechanisms including modulation by a family of interferon regulatory factors (IRFs) synthesised by host cell. IFNs activatemacrophage, induce B cell to switch immunoglobulin type, alter T helper response, inhibitcell growth, promoteapoptosis and induce an antiviral state in uninfected cell. The therapeutic potential of the IFNs is currently the focus of intense attention in a number of virus-associated diseases, tumours and autoimmune disorder.