Intraperitoneal injection of synthetic bacterial lipopeptides does not cause a rise in circulating inflammatory cytokines

The production of TNF-alpha, IL-1 and IL-6 was measured in mice after i.p. injections of the synthetic bacterial Lipopeptide Pam3Cys-Ala-Gly, a potent macrophage and B cell activator in vitro. Only minor amounts of IL-6 and no TNF-alpha were detectable in the serum of mice injected with 10 or 100 micrograms of Pam3Cys-Ala-Gly. Lipopeptide concentrations up to 1000 micrograms failed to induce IL-1, and TNF-alpha production and serum IL-6 levels were only slightly elevated. In contrast to Pam3Cys-Ala-Gly, i.p. injections of LPS were accompanied by high levels of the inflammatory cytokines TNF-alpha, IL-1 and IL-6 suggesting fundamental differences of the mode of action of these two substances when applied in vivo.