Gamma interferon priming of mouse and human macrophages for induction of tumor necrosis factor production by bacterial lipopolysaccharide

Priming of macrophages from both murine and human sources by recombinant immune interferons from Escherichia coli (r-IFN-gamma s) and activation by lipopolysaccharide (LPS) resulted in the production of tumor necrosis factor (TNF). r-IFN-gamma alone did not induce TNF production by macrophages; for this to occur, the second signal provided by small amounts (nanograms) of LPS was required. The small amounts of LPS alone were insufficient to activate the macrophages for TNF production. Priming by r-IFN-gamma was not necessary when larger amounts of LPS were employed, although an enhancement of yield resulted. Priming could also be demonstrated in vivo. Inoculation of r-IFN-gamma into mice resulted in increased yields of TNF following LPS challenge 12 hours later.