Induction of a tumor necrosis factor-like activity by Nocardia rubra cell wall skeleton

Nocardia rubra cell wall skeleton (N-CWS) stimulated adherent cells harvested from the peritoneal cavities of thioglycollate-treated mice to produce cytotoxic activity. Depletion of macrophages from the adherent cells by 2-chloroadenosine or silica abrogated the production of this cytotoxic activity, whereas treatment of the adherent cells with anti-Thy-1.2 antibody and complement did not. This suggested that macrophages were the producer cells of the activity. Cytotoxic activity became detectable as early as 2 h after N-CWS treatment and reached peak activity at 9 h, then declined to a lower level, indicating rapid onset without persistent effects. N-CWS-induced cytotoxic factors have a fairly narrow temperature range, pH optimum for storage, and are sensitive to pronase and trypsin. By using column chromatography, N-CWS-induced cytotoxic factors were compared in detail with tumor necrosis serum obtained from Bacillus Calmette-Guérin endotoxin-treated mice. Both toxins were found to be nearly identical with respect to their behavior in ion-exchange, gel filtration, and concanavalin A affinity columns. N-CWS also induced human peripheral blood lymphocytes to release cytotoxic activity. Monocytes predominantly participated in production of this activity as confirmed by treatment with monoclonal antibody and complement. The cytotoxic activity was completely neutralized by anti-human tumor necrosis factor antiserum, but not by anti-human lymphotoxin antiserum. The fact that human peripheral blood lymphocytes release tumor necrosis-like factors after stimulation with N-CWS might account for the antitumor effects of this agent.