PRINCIPLES OF TOXICOLOGY

10 Immunotoxicity: Toxic Effects on
the Immune System
IMMUNOTOXICITY: TOXIC EFFECTS ON THE IMMUNE SYSTEM
STEPHEN M. ROBERTS and LOUIS ADAMS
This chapter discusses
• Basic elements and functioning of the immune system
• Types of immune reactions and disorders
• Clinical tests to detect immunotoxicity
• Tests to detect immunotoxicity in animal models
• Specific chemicals that adversely affect the immune system
• Multiple chemical sensitivity
10.1 OVERVIEW OF IMMUNOTOXICITY
Exposure to a variety of chemicals and biological agents has been implicated in the onset of symptoms
of immune origin, including acute and chronic respiratory distress, dermal reactions, and manifestations
of autoimmune disease. The types of substances associated with immune system effects is
extraordinarily diverse, and include chemicals found in occupational and environmental settings,
infectious materials, certain foods and dietary supplements, and therapeutic agents. As discussed in
this chapter, dysregulation of the immune system by toxicants can lead directly to adverse health effects,
as well as rendering the body more susceptible to infectious disease and cancer.
The immune system is highly complex, with many facets poorly understood. Because of this,
assessment of potential immunotoxic effects of drugs, chemicals, and other agents is not a simple task.
Often, measurement of a variety of components of the immune system and/or their functionality is
required to gain an appreciation of the likelihood of immune dysfunction from drug or chemical
exposure. Increasingly, there is realization that the immune system may be among the most sensitive
target organs for toxicity for many chemicals and, as a result, merits special attention.
10.2 BIOLOGY OF THE IMMUNE RESPONSE
The immune system has evolved primarily to defend the body against the invasion of microorganisms,
although normal immune function is important in regulating and sustaining the internal environment
as well, such as recognition and removal of malignant cells. There are two types of immunity: natural
immunity (also termed innate immunity) and acquired immunity (also termed specific immunity).
Natural immunity is nonspecific in that it is directed to a wide variety of foreign substances, and is
rarely enhanced by prior exposure to these substances. Natural immunity arises from several mechanisms,
including complement, natural-killer (NK) cells, mucosal barriers, and the unique activity of
Principles of Toxicology: Environmental and Industrial Applications, Second Edition, Edited by Phillip L. Williams,
Robert C. James, and Stephen M. Roberts.
ISBN 0-471-29321-0 © 2000 John Wiley & Sons, Inc.
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