Interleukin-1 and Interferon-α Augment Interleukin-2 (IL-2) Production by Distinct Mechanisms at the IL-2 mRNA Level

Abstract

The production of interleukin-2 (IL-2) by phytohemaglutinin (PHA)-stimulated cells of human leukemia T cell line MOLT-16 can be significantly increased by interleukin-1 (IL-1) or interferon-α (IFN-α). The enhancing effect of IL-1 and IFN-α on IL-2 production was studied at the IL-2 mRNA level. We show that IL-1 enhances considerably and transiently, with the maximum level between 1 and 2 hr after stimulation, the expression of IL-2 mRNA in the PHA-stimulated cells. The level of IL-2 mRNA declined rapidly within 4 to 6 hr after stimulation in both PHA- and PHA plus IL-1-stimulated cell cultures. On the contrary, IFN-α does not elevate the level of IL-2 mRNA above the level in PHA-stimulated cultures, but maintains an enhanced level of IL-2 mRNA in the activated cells for more than 6 hr after stimulation. These observations correlate well with the kinetics of IL-2 protein production into the culture media. The results thus suggest that IL-I and IFN-α may exert an enhancing effect on IL-2 production by distinct mechanisms. In addition, none of the five other lymphokines tested (i.e., IL-2, IL-3, IL-4, IL-5, and IL-6) had any significant effect on IL-2 mRNA expression in the activated MOLT-16 cells.