Production of interleukin-6 from macrophages by MDP-Lys (L 18), romurtide.

N2-[(N-Acetylmuramoyl)-L-alanyl-D-isoglutaminyl-N6-stearoyl-L-lysine [MDP-Lys(L18), romurtide] is an immunopotentiating substance. In addition to neutrophilic leukocytosis, the effects previously found after the administration of this compound in both mice and humans were thrombocytosis and elevated levels of colony-stimulating factor (CSF) in peripheral blood. Although the exact mechanism of thrombopoiesis is not yet known, evidence has been accumulating that interleukin-6 (IL-6) plays an important role in the maturation of megakaryocytes, and the administration of IL-6 has been reported to induce a significant increase in blood platelets associated with promotion of megakaryocyte maturation. We measured the IL-6 levels in the culture supernatants of peripheral blood mononuclear cells (PBMCs), adherent cells and nonadherent cells in the presence of romurtide. Significant augmentation of IL-6 from PBMCs and adherent cells, but not nonadherent cells, was observed in the presence of romurtide in vitro.