Immunotoxicology

The immune system is a complex set of cellular and soluble mediators that protects the body against infectious agents and neoplasias. Innate immune responses do not require antigen recognition or clonal expansion and thus provide a rapid defence response against pathogenic organisms. The adaptive immune response is more complex, requiring recognition of foreign antigens via cell-surface receptors, production of growth factors, proliferation of antigen-specific lymphocytes and activation of effector mechanisms that are ultimately directed against infectious agents or cancerous cells. While immune responses are usually beneficial, hypersensitivity reactions and autoimmune diseases are examples of inappropriate responses that may occur in genetically susceptible individuals following exposure to an environmental trigger. Immunotoxicology is the subdiscipline of toxicology that focusses on the unintended effects of chemical exposure on the immune system. There is extensive evidence to suggest that following exposure to particular chemicals unintended immunosuppression, unintended immunostimulation, hypersensitivity or autoimmunity may occur. Chemical-induced modulation of the immune system may result in adverse outcomes such as increased incidences of infectious or neoplastic diseases, allergy/asthma or autoimmune diseases. This chapter presents an overview of immune responses and how these responses may be affected by xenobiotics.