Effects of environmental toxins on lymphocyte function: studies in rhesus and man

The immune system is a potential target of environmental toxins. Impairment of immune function could have a disastrous effect upon the affected individual. We had the unique opportunity to study the results of a prolonged exposure to TCDD (2,3,7,8-tetrachlorodibenzo-P-dioxin) in rhesus monkeys and their offspring. Subsequently, we performed similar studies on humans exposed to the nematode pesticide, Aldicarb. This report summarizes those previous studies. In the monkeys, no major deficits of the immune system were found and the animals did not have excessive numbers of infections. However, at higher doses of dietary TCDD (25 ppt), only 22% of the offspring survived to 1 year of age. Thus, the failure to demonstrate effects on the young may simply relate to the essential equivalence of the lethal to an immunosuppressive dose. In humans, exposure to the acetylcholinesterase inhibitor, Aldicarb, was received through contaminated well water. The known exposure was for at least 1 year and could have been as long as 5 years. Various tests of the immune system, including lymphocyte subset counts, proliferative responses, total immunoglobulin levels and specific antibody responses did not reveal immunodeficiency. Increases in the numbers of CD8 positive T lymphocytes was observed. There was no evidence of any increase in clinical illness in the exposed compared with the control group.