Heterogeneity of Human Gamma Interferon Preparations: Evidence for Presence of Alpha Interferon*

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Abstract
Human gamma interferon (HuIFN-γ) preparations induced with several mitogens (Staphylococcal enterotoxin A, Phytohemagglutinin, or Pokeweed mitogen) had low levels of cross-species antiviral activity on bovine cells (∼1-5%) and were not neutralized by antisera to either human interferon alpha (HuIFN-α) or beta (HuIFN-β). After purification on controlled pore glass beads (CPG) these preparations could be fractionated into a minor component which was highly active on bovine cells and a major component that was virtually inactive on bovine cells. The highly cross-active component was pH2 stable and was neutralized by an anti-HuIFN-α antiserum, while the major, lowly cross-active component was pH2 labile and was not neutralized by either anti-HuIFN-αor HuIFN-β antisera. Chromatography of a CPG-purified mitogen-induced IFN preparation on anti-HuIFN-α Sepharose showed that, while the large majority of HuIFN-γ preparations passed through the column, a minor component was retained and eluted at pH2. Thus, human leukocyte suspensions stimulated by mitogens produced predominantly HuIFN-γ, but also produce some HuIFN-α.