(IFNs) were first discovered in 1957 by Isaacs and Lindenman as an activity which was inducible by heat killed influenza virus in chick chorioallantoic
membranes and could potently inhibit infection of fresh chick chorioallantoic membranes with live virus. It is composed of a family of distinct, acid stabile proteins which are highly similar in amino acid sequence and structure.
Persons with disorders of the interferon system are more susceptible to viral and bacterial diseases. Those with interferon production deficiencies are more susceptible to diseases caused by viruses such as HBV. Chronic hepatitis B virus infection acquired
in later life is also associated with a defect in interferon production. Patients with defects in IFNα, IFNβ and IFNλ, production or action are exquisitely susceptible to viral diseases such as herpes simplex encephalitis.