HEALTH EFFECTS|Immunotoxicity Definitions

Immunotoxicity Definitions
Immunotoxicity is defined as adverse effects on the functioning of the immune system that result from exposure to chemical substances. Altered immune function may lead to the increased incidence or severity of infectious diseases or cancer, since the immune system’s ability to respond adequately to invading agents is suppressed. Identifying immunotoxicants is difficult because chemicals can cause a wide variety of complicated effects on immune function. Observations in humans and studies in rodents have clearly demonstrated that a number of environmental and industrial chemicals can adversely affect the immune system. Exposure to asbestos, benzene, and halogenated aromatic hydrocarbons such as polybrominated biphenyls (PBBs), polychlorinated biphenyls (PCBs), and dioxins (TCDD) can lead to immunosuppression in humans. Toxic agents can also cause autoimmune diseases, in which healthy tissue is attacked by an immune system that fails to differentiate self-antigens from foreign antigens. For example, the pesticide dieldrin induces an autoimmune response against red blood cells, resulting in hemolytic anemia.

Also considered to be immunotoxicants, allergens are compounds that stimulate the immune system and can cause hypersensitivity reactions or allergies. Many chemicals induce allergic reactions in humans and experimental animals, producing a variety of clinical manifestations, such as asthma, rhinitis, and anaphylaxis. The industrial chemical toluene diisocyanate (TDI) and metals such as nickel and beryllium are notable examples of allergenic agents.

For further general information on chemicals and immunotoxicity, see the following references:

Dean, J., M. Murray, and E. Ward. Toxic Responses of the Immune System. Chapter 9 in Casarett and Doull's Toxicology, edited by C. Klaassen, M. Amdur, and J. Doull. New York: Pergamon Press, 1996.

Holladay, S. D., and M. Luster. Chemically-Induced Alterations in the Developing Immune System: The Wildlife/Human Connection. Environmental Health Perspectives 104 (Supplement 4): 809- 814. 1996.

Krzystyniak, K. Approaches to the Evaluation of Chemical Induced Immunotoxicity. Environmental Health Perspectives 203(9): 17-23. 1995.

Luster, M. I. Immunotoxicology: Clinical Consequences. Toxicology and Industrial Health. 12(3): 533-535. 1996.

Luster, M. I., and G. Rosenthal. Chemical Agents and the Immune Response. Environmental Health Perspectives. 100: 219-236. 1993.

Office of Technology Assessment. Identifying and Controlling Immunotoxic Substances. Washington, D.C.: Government Printing Office, 1991.

Thomas, P. T. Pesticide-Induced Immunotoxicity: Are the Great Lakes at Risk? Environmental Health Perspectives. 103 (Supplement 9): 55-61. 1995.