Comparative antiproliferative activity in vitro of natural interferons alpha and beta for diploid and transformed human cells.

The relative antiproliferative activity of natural interferons alpha and beta 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 beta produced greater than 20% growth inhibition in 22 cells (88%), and interferon alpha produced 20% growth inhibition in 9 cells (36%). Only Daudi (Burkitt's lymphoma) cells were consistently more inhibited by interferon alpha. In the other 24 human cells, the effect of interferon beta was greater or equal to interferon alpha. Although no tissue specificity for interferon beta was evident, interferon alpha generally had greater antiproliferative effects in cells of hematopoietic origin. The effect of interferon alpha was usually established by 72 hr with little further growth inhibition at 120 hr. Conversely, interferon beta 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.