Field studies in humans designed to detect immunomodulation from exposure to xenobiotics present challenging problems to epidemiologists and immunotoxicologists. Exposed and control groups must be carefully selected, exposure to the xenobiotic must be sufficiently high and well documented, and the control group should be as similar as possible to the exposed. Immune biomarkers/function tests in an individual may be influenced by sunlight exposure, medication, illness and use of recreational drugs; all of these potential "confounding factors" must be taken into account. Sample acquisition usually is performed at sites geographically distant from the controlled environment of an investigator's laboratory, yielding an assortment of new problems that would not occur in clinical or hospital situations. Regulations and guidelines concerning the transport of biological samples and potential HIV and HBV exposure to personnel must be adapted to field conditions. In addition to the above, test batteries used must be designed to eclectically detect modulation of the immune system. For example, in an investigation of ethical narcotics production workers, NIOSH investigators found both evidence of immunosuppression (significantly decreased percentages of T helper-inducer [CD4+] cells), evidence of opiate-class sensitization (lowered epicutaneous titration thresholds), elevated anti-morphine IgG, and an elevated prevalence of asthma. In a non-comprehensive design directed to detect only immunosuppression as an expected outcome, much significant information would have been left undetected.
The Toxicologist. Society of Toxicology 33rd Annual Meeting, March 13-17, 1994, Dallas, Texas