Environmental Influences on Autoimmunity and Autoimmune Diseases

For some autoimmune diseases, little is known about environmental factors involved in the initiation or progression of the disease. For other diseases, however, considerable research has been conducted on one or more types of exposures. Most epidemiologic studies of environmental influences have focused on multiple sclerosis, rheumatoid arthritis, scleroderma, systemic lupus erythematosus, and small vessel vasculitis, but experimental studies using murine models of these diseases is limited (Table 25.1). 

For type 1 DM, the concordance rate for identical twins is only 25—50% and environmental influences must have an important role. Type 1 DM involves an autoimmune attack on the pancreatic /3 cells. Antibodies to islet cell antigens are detected in up to 80% of patients with type 1 DM shortly after diagnosis or even prior to the onset of clinical disease. Type 1 DM is associated with specific human leukocyte antigen (HLA) alleles, especially at the B and DR loci, and the HLA complex is known to play critical roles in the immune response. However, the trigger for the immune response remains unknown. In about 10% of new cases of type 1 DM, there is no evidence of autoimmune insulitis. The ADA and the World Health Organization (WHO) therefore subdivide this disease into autoimmune (lA) and idiopathic (IB) subtypes. 

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