[The environment and autoimmunity--from external causes to inner conflicts]

Autoimmune disorders result from a breakdown of immunologic tolerance leading to an immune response against self-molecules. In most instances the events that initiate the immune response to self-molecules are unknown, but a number of studies suggest associations with environmental and genetic factors and certain types of infections. The concordance of autoimmune diseases among identical twins is virtually always less than 50%, often in the 25-40% range. This observation, as well as epidemic clustering of some autoimmune diseases following xenobiotic exposure, reinforces the thesis that autoimmune disease is secondary to both genetic and environmental factors. In addition, because of individual genetic susceptibilities based not only on major histocompatibility complex differences but also on differences in toxin metabolism, lifestyles, and exposure rates, individuals will react differently to the same chemicals. With these comments in mind it is important to note that there have been associations of a number of xenobiotics with human autoimmune disease, including mercury, iodine, vinyl chloride, canavanine, organic solvents, silica, L-tryptophan, particulates, ultraviolet radiation, and ozone. In addition, there is discussion in the literature that raises the possibility that xenobiotics may also exacerbate an existing autoimmune disorder. In this article these issues are discussed, in particular, the evidence for the role of environmental agents in the initiation or progression of autoimmune conditions. With the worldwide deterioration of the environment, this is a particular important subject for human health. This is best illustrated by the epidemics of eosinophilic myalgia syndrome with shared characteristics that occurred about 20 years ago. Another example is the toxic oil syndrome of Spain in 1981 involving cooking oil led to both acute and chronic disease as well as formation of auto-antibodies to collagen, DNA, and skeletal muscle. Currently the question is risen whether there is a link between environmental estrogens and autoimmune disorders, especially since these illnesses are reported possibly more frequent. Yet for the time being, an answer is not available, since the current state of science with respect to autoimmunity and environmental agents is still in the early stages of hazard identification.