Effect of interferon on the induction of human monocyte secretion of interleukin-1 activity

This study investigates the effect of interferons on the induction of human monocyte secretion of interleukin-1 (IL-1) activity by lipopolysaccharides (LPS). Monocytes do not spontaneously produce IL-1 and the addition of interferons to the culture does not lead to detectable secretion. Addition of LPS alone induces the release of measurable amounts of IL-1 activity. The addition of low doses (1-10 units/ml) of alpha, beta, or gamma interferon to the LPS-stimulated cultures further increases this secretion by 50%. The addition of 1000 units/ml of alpha or beta interferon leads to inhibition of IL-1 release. By contrast, gamma interferon is a dose dependent enhancer of IL-1 release. The effect of gamma interferon is on the production of IL-1 and is not an enhancement of IL-1 activity in the biological assay. Results demonstrate that addition of gamma interferon to monocytes increases the rate of secretion of IL-1 by these cells. Gamma interferon also appears to abrogate the loss in the ability of monocytes to produce IL-1 activity after overnight culture. This last result parallels the maintainence of the expression of the HLA-DR surface marker on monocytes by gamma interferon. These results may help define a mechanism involving IL-1 generation which could have bearing on the in vivo pyrogenic effects of purified gamma interferon.