EPIDEMIOLOGY STUDIES IN IMMUNOTOXICITY EVALUATIONS

Studies in humans designed to detect immunomodulation from exposure to xenobiotics present challenging problems to epidemiologists and immun otoxicologists. Exposed and control groups must be carefully selected, exposure to the xenobiotic must be sufficiently high and well-documen ted, and the referent group should be as similar as possible to the ex posed. Immune markers/functional tests in an individual may be influen ced by sunlight exposure, medication, illness and use of recreational drugs; all of these potential confounding factors must be addressed. S ample acquisition is usually performed at sites geographically distant from the controlled environment of an investigator's laboratory, yiel ding an assortment of new problems that would not occur in clinical or hospital situations. Regulations and guidelines concerning the transp ort of biological samples and potential hazards of HIV and HBV exposur es to personnel must be adapted to field conditions. Since the applica tion of immunotoxicological techniques to populations exposed to xenob iotics is relatively new, and the ability to measure an increasing num ber of immune biomarkers of activation, suppression, autoimmunity or h ypersensitivity is rapidly expanding, there are difficulties in the in terpretation of statistically positive results (sometimes within the n ormal range) and their potential health significance. Finally, both bi ological and methodological factors complicate the assessment of dose- response/concentration-effect relationships in human immunotoxicity st udies, and traditional dose-response relationships may not always be p resent. Published by Elsevier Science Ireland Ltd.