[Inhibitory effect of Staphylococcus aureus on the growth of rat sarcoma]

We have studied the effect upon the growth of a transplantable rat sarcoma, of an intraperitoneal inoculation of peritoneal exudate cell (PEC), spleen cells (SC) and non-adherent spleen cells (N-ASC) obtained from S. aureus previously inoculated rats and the same cells from normal rats (NPEC, NSC, NN-ASC). Inbred, adult rats were inoculated with 800 x 10(6) bacteria, killed by tyndalization. After 7 days, treated and normal animals were sacrificed and PEC, SC and N-ASC were obtained. Different groups of animals were inoculated with these cell populations. Simultaneously the rats received a s.c. inoculum of a transplantable sarcoma (S-E 100). Tumor size was measured on days 4, 7, 14, 21 and 28 after tumor challenge. A significant tumor growth inhibition was found with all three cell populations, but no effect was observed with normal cells. Tumor size on different days and tumor growth curves clearly demonstrate this effect. We conclude that Staphylococcus aureus inoculum as well as the cells from animals previously challenged with the bacteria induce tumor growth inhibition. The possibility that protein A of S. aureus may be involved in this phenomenon, or that the mechanism of tumor growth inhibition is mediated by an activation of different cell populations is discussed.