J. Biol. Chem., Vol. 265, Issue 12, 7036-7041, 04, 1990
Interferon gamma and interleukin 2 synergize to induce selective monokine expression in murine peritoneal macrophages
S Narumi, JH Finke and TA Hamilton
Research Institute, Cleveland Clinic Foundation, Ohio 44195-5069.
We have examined the effects of interleukin 2 (IL-2) treatment either alone
or in combination with interferon (IFN) gamma or beta on the expression of
several activation associated genes (e.g. tumor necrosis factor alpha (TNF
alpha), IFN-inducible 10-kDa protein (IP-10] in murine peritoneal
macrophages. IL-2 alone did not induce the expression of either gene while
IFN gamma or IFN beta had a modest inductive effect on IP-10 but no effect
on TNF alpha expression. When either form of IFN was used in combination
with IL-2 there was a marked synergistic induction of both mRNAs. IFN gamma
and IL-2 were maximally effective when both agents were added
simultaneously, and induced mRNA expression declined over a 24-h period in
cells pretreated with IFN gamma prior to addition of IL-2. Expression of
both genes following combination lymphokine treatment was mediated by
increased transcriptional activity. The responses to all three lymphokines
were dose dependent; the concentration requirement for IL-2 indicated
interaction with an intermediate or low affinity receptor. The expression
of both monokine genes was transient and was comparable although not
identical to that seen in cells stimulated with lipopolysaccharide. IFN
gamma and IL-2 could synergize to stimulate the expression of either TNF
alpha or IP- 10 mRNA using sequential non-overlapping treatment periods
regardless of the order in which the two stimuli were applied to the cells.
The effect of either agent alone induced a transient (1-5 h) responsive
state with respect to subsequent stimulation with the second agent.
Expression of both monokine genes in response to IFN gamma/IL-2 treatment
was independent of protein synthesis as cycloheximide did not inhibit the
accumulation of specific mRNA. Interestingly, the combination of IL-2 and
cycloheximide was as effective as IFN gamma and IL-2 together. In concert,
these results indicate that both IFN and IL- 2 generate independent
intracellular signals which alone are incapable of inductive effect but
which are potent activators of inflammatory gene expression when
coincidentally expressed.