Elevation by muroctasin of the serum level of the complement subcomponent C1q in mice and of its biosynthesis by cultured mouse peritoneal macrophages.

Augmentative effects of muroctasin (N2-[(N-acetylmuramoyl)-L-alanyl-D-isoglutaminyl]-N6-stearoyl-L-lysine, (MDP-Lys(L18] on the production of a subcomponent of the first complement component, C1q, in mice were examined. The serum level of C1q in mice treated subcutaneously with muroctasin was found to be elevated significantly at 24 h (p less than 0.1) and 48 h (p less than 0.01). At 24 h, samples of peritoneal macrophages were derived from mice, and incubated with Dulbecco's Modified Eagle Medium (MEM) at 37 degrees C for 24 h. At 19 h of incubation, the C1q concentration in the supernatant of the culture also increased significantly (p less than 0.05). Moreover, when the peritoneal macrophages from non-treated mice were cultured in MEM containing muroctasin (0.001 microgram/ml), the amount of C1q in the culture supernatants also increased significantly 3 h (p less than 0.01) after cultivation. These results indicate that muroctasin activated C1q generation by macrophages in mice through direct and/or indirect mechanisms.