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 sp ecies may be altered after perinatal exposure to immunotoxic environme ntal contaminants. However, limited information is available regarding appropriate tests that may adequately detect developmental immunotoxi c compounds. Experiments in which pregnant laboratory rodents were exp osed to a variety of immunotoxic environmental agents indicate that fe tal thymus and liver immune cells may be quantitatively and qualitativ ely altered by immunotoxicant exposure and, thus, may serve as sensiti ve markers of developmental immunotoxicant exposure: In particular, de pression of fetal thymic cell counts appears to be a common event foll owing gestational exposure to immunotoxicants that produce this respon se in adult animals. Total hematopoietic cell counts in fetal liver, h owever, may be a poor indicator of immunotoxicant exposure. Altered ma rker 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 i mmunosuppression in adults may also be appropriate for the detection o f developmental immunotoxic agents.