The relative antiproliferative activity of natural interferons α and β was compared in 43 in vitro assays of 25 human cell lines or strains. After 120 hr of continuous exposure to 100 units/ml, interferon β produced >20% growth inhibition in 22 cells (88%), and interferon α produced 20% growth inhibition in 9 cells (36%). Only Daudi (Burkitt's lymphoma) cells were consistently more inhibited by interferon α. In the other 24 human cells, the effect of interferon β was greater or equal to interferon α. Although no tissue specificity for interferon β was evident, interferon α generally had greater antiproliferative effects in cells of hematopoietic origin. The effect of interferon α was usually established by 72 hr with little further growth inhibition at 120 hr. Conversely, interferon β often had a greater antiproliferative effect at 120 than at 72 hr. These findings support the hypothesis that various interferons may differ in their biological, cell-regulatory, and clinical effects.

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Assisted by grants from the Veterans Administration and the American Cancer Society. Data presented in part at the Fifth International Congress of Virology, Strasbourg, France, August 1981 (4).

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