How do interferons protect us?

Hint: They are a type of protein produced by the cells in our body in response to an infection. They are produced when the immune system is triggered by external pathogens or cytokines. When triggered, they induce numerous molecular changes that affect cellular responses including cell growth and inflammation.

Complete answer:
The interferons are of two types. Type I interferons and Type II interferons. Interferon alpha and interferon beta are of type I. They are particularly potent as antiviral agents. They are not expressed in normal cells but when a cell is infected by a virus, production and release of interferon occurs. The interferon binds to target cells and eliminates them. Both DNA and RNA viruses can induce production of interferon.
Type II interferon or Interferon-gamma (immune interferon) is produced by certain activated T-cells and Natural killer cells. They are produced when antigen or mitogen stimulation of lymphocytes occur.
The interferons do not directly kill the virus. Instead, they induce the virus infected cells and other cells nearby to produce proteins which will stop the replication and spread of virus within the body.

Note:
Interferons are produced commercially through DNA recombinant technology for clinical use. Since they have both antiviral and anticancer activities, they are used to treat many diseases in the clinical field. Alpha-interferon has been approved for treating hairy-cell leukaemia and Kaposi sarcoma, a cancer that occurs in AIDS patients. Gamma interferon is mainly used as an immune stimulant in cancer patients. It is also used to treat chronic granulomatous disease, a hereditary condition in which white blood cells fail to kill the bacteria.