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 systems 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.
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