Interferons: purification and physicochemical aspects.

Antiviral interferon activity in any one species can be exhibited by a variety of substances that differ in their physical and chemical properties, but the nature of these differences is not understood. Conditions that can lead to the formation of diverse types of interferons have been outlined. Reasons have been adduced why, for certain purposes, purification of interferons is desirable or even necessary, and examples have been presented to show how and to what extent this has been achieved. In spite of some very high purification factors, not a single interferon has been obtained as a pure substance. Therefore, all available knowledge of physical and chemical properties has been obtained by indirect means.