Comparison of Interleukin 1 Release and Interleukin 1 mRNA Expression of Human Monocytes Activated by Bacterial Lipopolysaccharide or Synthetic Lipid A

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Abstract
Several of the biological effects of bacterial lipopolysaccharide (LPS) can be induced by the lipid A part of the molecule. Here we show that in human peripheral blood monocytes, synthetic E. coli lipid A is as effective as the whole LPS molecule in inducing the production of interleukin 1 (IL-1) bioactivity which remains associated to the cells (i.e. IL-1.alpha.). In contrast, LPS- but not lipid A-stimulated cells released the bioactive IL-1 produced into the culture supernatant (mainly IL-1.beta.). Northern blotting analysis demonstrated, however, that LPS and lipid A are equally effective in inducing the accumulation of IL-1.alpha. and IL-1.beta. mRNA. These data support the hypothesis that induction of IL-1 biosynthesis and activation of the secretory mechanism for IL-1 are independent phenomena.