Depressed humoral immunity and increased tumor incidence in mice following in utero exposure to benzo[alpha]pyrene.

Exposure of mice to a single small dose of benzo[a]pyrene in utero leads to a severe suppression of the anti-sheep erythrocyte plaque-forming response shortly after birth that persists into later life. There is also an 11- to 13-fold increase in the frequency of tumors in these mice at 56-78 wk of age compared to the untreated control group. Mice exposed to 150-R X-irradiation in utero, after an early immune suppresion, show recovery of the plaque-forming response with no increase in tumor incidence. The sustained suppression in immune status induced in mice by exposure to benzo[a]pyrene during fetal life may be related to an altered immune surveillance mechanism and a consequent increased susceptibility to tumor development.