Alterations in fetal thymic and liver hematopoietic cells as indicators of exposure to developmental immunotoxicants.

Recent studies indicate that immune development in humans and other species may be altered after perinatal exposure to immunotoxic environmental contaminants. However, limited information is available regarding appropriate tests that may adequately detect developmental immunotoxic compounds. Experiments in which pregnant laboratory rodents were exposed to a variety of immunotoxic environmental agents indicate that fetal thymus and liver immune cells may be quantitatively and qualitatively altered by immunotoxicant exposure and, thus, may serve as sensitive markers of developmental immunotoxicant exposure. In particular, depression of fetal thymic cell counts appears to be a common event following gestational exposure to immunotoxicants that produce this response in adult animals. Total hematopoietic cell counts in fetal liver, however, may be a poor indicator of immunotoxicant exposure. Altered marker expression in both fetal thymus and liver appears to be a highly sensitive indicator of gestational immunotoxicant exposure. Together, these reports suggest that immune tests with high predictability for immunosuppression in adults may also be appropriate for the detection of developmental immunotoxic agents.