Immunotoxicology can broadly be defined as "the science of poisons for the immune system". Thus, immunotoxic effects encompass a wide range of adverse health events reflecting untoward interferences between xenobiotics and the immune system.

A huge number of medicinal products and chemicals have been suspected or shown to induce histological changes in the main lymphoid organs including the thymus, the spleen, lymph nodes and Peyer's patches, and/or functional disturbances of the immune responsiveness resulting in impaired, enhanced or aberrant immune responses. These findings in preclinical immunotoxicology studies were sometimes associated with clinical significant adverse effects in treated or exposed human subjects.

The clinical experience accumulated over the years on the adverse effects of immunotoxicants clearly indicates that immunotoxicology encompasses 4 categories of immunotoxic effects, namely immunosuppression, immunostimulation, hypersensitivity ("allergy"), auto-immunity. The old and obviously obsolete classification into 2 categories: immunosuppression and immunostimulation, the latter further subdivided into hypersensitivity and auto-immunity, is no longer recommended as it absolutely does not take into account the clinical experience with human immunotoxicants.

Suggested readings

J. Descotes: An Introduction to Immunotoxicology. Taylor & Francis: London, 1998