Production of colony-stimulating factor from macrophages by muroctasin.

The effect of a muramyl dipeptide analog, N2-[(N-acetylmuramoyl)-L-alanyl-D-isoglutamyl]-N6-stearoyl-L-lysin e (MDP-Lys(L18), muroctasin), on the colony-stimulating factor (CSF) production was investigated in vitro. MDP-Lys(L18) stimulated murine peritoneal macrophages to induce CSF. However, the compound produced more CSF in the presence of both macrophages and T cell enriched fraction than in the absence of T cells. This phenomenon was found to be attributed to the fact that MDP-Lys(L18) also stimulated macrophages to induce interleukin 1 (IL-1) and the IL-1 induced CSF production by T cells. These findings suggest that macrophages may be the first target cells of MDP-Lys(L18) to produce CSF.