Natural host defence during oncogenesis. NK activity and dimethylbenzanthracene carcinogenesis.

In this study we determined the effect of administering the chemical carcinogen dimethylbenzanthracene (DMBA) on NK activity mediated by murine splenocytes. The intragastric administration of six weekly 1-mg doses of DMBA to 2- to 3-month-old mice either following a pituitary graft or not, resulted in a tumor incidence which was higher than 60%. The cellularity of the spleens decreased significantly after the third DMBA feeding and the NK activity of these spleens was selectively suppressed.