Are environmental pollutants threatening the human immune system? Researchers are rapidly approaching definitive answers to this question, with the aid of biologic markers--sophisticated assessment tools that could revolutionize detection and prevention of certain diseases. This volume, third in a series on biologic markers, focuses on the human immune system and its response to environmental toxicants. The authoring committee provides direction for continuing development of biologic markers, with strategies for applying markers to immunotoxicology in humans and recommended outlines for clinical and field studies. This comprehensive, up-to-date volume will be invaluable to specialists in toxicology and immunology and to biologists and investigators involved in the development of biologic markers.