Stimulation of one particular subset of natural killer cells by peptidoglycans extracted from gram-positive bacteria

Peritoneal nonspecific cytotoxicity was stimulated by ip injection into C57BL/6 or (C57BL/6 X C3H/He)F1 mice of Staphylococcus aureus peptidoglycan (PGS), which possessed an antitumor effect, and of Micrococcus lysodeikticus peptidoglycan (PGM), which was ineffective against tumors. The natural killer (NK) cell populations elicited by both peptidoglycans had the same phenotype: Thy 1.2+, T200+, Ly 5.1+, Qa5+, and Ly 2.2-. In vivo treatment with sheep anti-mouse beta interferon serum abrogated this effect. The fluids from phorbol myristate acetate-stimulated murine EL 4 thymoma cells enhanced this particular NK activity, and thus PGM-induced effector cells became able to kill solid tumor cells. In conclusion, both PGS and PGM elicited the same particular subset of NK cell populations, and the peptidoglycan structure can play an important role in the intensity of this response.