In vitro and in vivo augmentation by muroctasin of the production of the third component of complement by murine macrophages.

In vitro and in vivo examinations were carried out to assess the influence of N2-[(N-acetylmuramoyl)-L-alanyl-D-isoglutaminyl]-N6-stearoyl-L-lysine (MDP-Lys (L18), muroctasin) on the biosynthesis of the 3rd component of complement (C3) of murine peritoneal macrophages. The amount of C3 in the supernatant of the macrophages cultured in serum free minimal essential medium (MEM) was measured using the enzyme-linked immunosorbent assay (ELISA) system. The in vitro C3-production by the cultured macrophages was inhibited by treatment with cycloheximide, but promoted dose-relatedly with MDP-Lys (L18). The in vitro ability of peritoneal macrophages derived from mice treated subcutaneously with MDP-Lys (L18) to produce C3 was also augmented significantly: a diphase pattern of production was noticed during the 120 h following administration. According to the immunoelectrophoretic analysis, C3 thus produced by cultured peritoneal macrophages was identical with the native C3 in serum.