The effect of carcinogens on immune responses in the guinea-pig.

The short-term and long-term effects of the administration of 2 carcinogens, diethylnitrosamine and methylcholanthrene, on immunological responses in guinea-pigs have been investigated. The study was undertaken to examine the possibility that these carcinogens act in part through nonspecific immunosuppression. The results show that in the period immediately after commencement of carcinogen administration, one aspect of the delayed hypersensitivity reaction to tuberculin (induration) was decreased in the carcinogen treated animals as compared with the controls. This could possibly reflect a reaction to the immediate toxic effect of the chemicals. In the main long-term study, however, in which the immunological responses were tested 6-9 months after commencement of carcinogen treatment ( where the administration schedules, especially for diethylnitrosamine, could and did result in subsequent tumour induction), there was no immunodepression as evidenced by the results of delayed hypersensitivity reactions to tuberculin, immediate hypersensitivity reactions to ovalbumin, autoimmune reactions to testis and normal lymphocyte transfer tests. It is considered probable that the tumorigenic effect of these 2 compounds is due to their direct carcinogenic properties and is not aided by any substantial nonspecific immunosuppression.