In vivo and in vitro effects of Nocardia rubra cell wall skeleton on natural killer activity in mice.

The in vivo and in vitro effects of Nocardia rubra cell wall skeleton (N-CWS) on natural killer (NK) activity of spleen and peritoneal lymphocytes of C57BL/6 mice were studied. The NK activity of spleen and peritoneal lymphocytes against YAC-1 lymphoma cells and cultured B-16 melanoma cells peaked at 3 days after intraperitoneal or intravenous administration of N-CWS, and returned to the normal value 7 days later. The NK activity of spleen lymphocytes was augmented by in vitro incubation with N-CWS. The appropriate concentration of N-CWS for the in vitro stimulation of NK activity in spleen lymphocytes was 2-5 micrograms/ml.