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The effects of single or repeated Bacillus of Calmette and Guérin (BCG) treatment on the onset of tumors induced by the carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) injected at birth into Swiss mice were studied. Multiple doses of BCG, given at regular intervals significantly lowered the incidence of carcinogen-induced tumors. The DMBA-induced lung adenomas did not differ morphologically from the ones that appeared in mice simultaneously treated with both DMBA and BCG.

The present paper describes the effects of repeated administration of rabbit anti-mouse lymphocyte serum (ALS) or normal rabbit serum (NRS) on tumours induced in Charles-River mice by 7,12-dimethylbenz(α)anthracene (DMBA) given at birth. ALS or NRS were given either at the time of DMBA administration and subsequently at weekly intervals for the first 10 weeks of life, or at daily intervals for 7 days during the first, second, third or fourth week of life. The incidence and histology of the tumours were studied. It was found that treatment of very young mice with ALS greatly reduced the mean survival time of mice and significantly increased the incidence of malignant lymphoma. The incidence of lung tumours was found to be significantly increased in the animals injected with ALS during the second week of life.Treatment with ALS in the other experimental groups gave results essentially similar to those observed in DMBA control and NRS treated mice.