Prenatal HgCl2Exposure Alters Fetal Cell Phenotypes

Risk of autoimmune disease: challenges for immunotoxicity testing

Autoimmunity represents a potentially diverse and complex category among the range of adverse outcomes for detection with immunotoxicity testing. For this reason, the risk of autoimmune disease is discussed in this overview chapter with additional mention among the later specific protocol chapters. Improvements in clinical diagnostic capabilities and disease recognition have led to a more accurate picture of the extent of autoimmune diseases across different human populations. While the risk of any single autoimmune disease remains modest when compared with that of lung or heart disease, the cumulative prevalence of autoimmune diseases is both significant and increasing. Autoimmune diseases are usually viewed in the context of the damaged tissue or organ (e.g., as a thyroid, gastrointestinal, cardiovascular or neurological disease). But improved recognition that underlying immune dysfunction can connect the risks for these as well as other diseases is critical for optimizing risk assessment. Since autoimmune diseases are chronic in nature with many first appearing in children or in young adults, these diseases exert a serious impact on both health care costs and quality of life. This chapter provides a discussion of the issues that should be considered with immunotoxicity testing for risk of autoimmunity.

Developmental immunotoxicology: focus on health risks

Developmental immunotoxicity (DIT) has gained attention with the recognition that many chronic diseases of increasing incidence feature immune dysfunction as a component of the disease. The maturing immune system represents a vulnerable target for toxicants as it progresses through a series of novel prenatal and perinatal events that are critical for later-life host defense against a wide array of diseases. These critical maturational windows display a particular sensitivity to chemical disruption with the outcome usually taking the form of persistent immune dysfunction and/or misregulation. For this reason, health risks are significantly increased following early life vs adult immunotoxic exposure. Additionally, DIT-associated health risks are not readily predicted when based on adult-exposure safety data or via the evaluation of an unchallenged immune system in developmental toxicity testing. The same toxicant [e.g., heavy metals, 2,3,7,8-tetraclorodibenzo-p-dioxin (TCDD)] may disrupt different immune maturational processes depending upon the specific developmental timing of exposure and the target organ dose at a given stage of development. Therefore, a single toxicant may promote different immune-associated diseases that are dependent upon the specific window of early life exposure, the gender of the exposed offspring, and the genetic background of the offspring. This perspective considers the linkage between early life chemical exposure, DIT, and the postnatal immune dysfunctions associated with a variety of childhood and adult diseases. Because DIT is linked to a majority of the most significant childhood chronic diseases, safety testing for DIT is a pivotal issue in the protection of children's health.

Potential for early-life immune insult including developmental immunotoxicity in autism and autism spectrum disorders: focus on critical windows of immune vulnerability

Early-life immune insults (ELII) including xenobiotic-induced developmental immunotoxicity (DIT) are important factors in childhood and adult chronic diseases. However, prenatal and perinatal environmentally induced immune alterations have yet to be considered in depth in the context of autism and autism spectrum disorders (ASDs). Numerous factors produce early-life-induced immune dysfunction in offspring, including exposure to xenobiotics, maternal infections, and other prenatal-neonatal stressors. Early life sensitivity to ELII, including DIT, results from the heightened vulnerability of the developing immune system to disruption and the serious nature of the adverse outcomes arising after disruption of one-time immune maturational events. The resulting health risks extend beyond infectious diseases, cancer, allergy, and autoimmunity to include pathologies of the neurological, reproductive, and endocrine systems. Because these changes may include misregulation of resident inflammatory myelomonocytic cells in tissues such as the brain, they are a potential concern in cases of prenatal-neonatal brain pathologies and neurobehavioral deficits. Autism and ASDs are chronic developmental neurobehavioral disorders that are on the rise in the United States with prenatal and perinatal environmental factors suspected as contributors to this increase. Evidence for an association between environmentally associated childhood immune dysfunction and ASDs suggests that ELII and DIT may contribute to these conditions. However, it is not known if this linkage is directly associated with the brain pathologies or represents a separate (or secondary) outcome. This review considers the known features of ELII and DIT and how they may provide important clues to prenatal brain inflammation and the risk of autism and ASDs.