29.11B: Autoimmune Diseases
Autoimmune diseases are an inappropriate immune response against tissues in the body.
- Describe autoimmune diseases
Key Points
- Autoimmune diseases arise from an immune system that does not function properly.
- The common cause hypothesis of autoimmune diseases describes how autoimmune diseases are triggered by genes located in the same regions on the chromosome.
- Despite genetic factors being involved in the onset of autoimmune disease, much is not know about the other causes of autoimmunity.
Key Terms
- autoimmune diseases : Arise from an inappropriate immune response of the body against substances and tissues normally present in the body.
- common cause hypothesis : Predicts that common disease-causing alleles, or variants, will be found in all human populations which manifest a given disease.
Autoimmune diseases arise from an inappropriate immune response of the body against substances and tissues normally present in the body. In other words, the immune system mistakes some part of the body as a pathogen and attacks its own cells. Autoimmune diseases are commonly considered complex immune disorders. While many autoimmune diseases are rare, collectively these diseases afflict millions of patients. Approximately 5–8% of the U.S. population suffers from this group of chronic, debilitating diseases. Despite their clinical diversity, they have one similarity, namely the dysfunction of the immune system. It is suspected that genetic defects play a role in the etiology of these diseases.
Causes and Treatments
Modern high throughput technologies, like mRNA microarrays, have enabled researchers to investigate diseases at a genome-wide level. In contrast to classical inherited genetic diseases, like sickle cell anemia, autoimmune diseases are not caused by the defect of a single gene, but by the dysfunction of the complex interaction of a group of genes. Although no autoimmune disease has been completely analyzed, there has been tremendous success in recent years in identifying major players in the development of autoimmune diseases. There are over 50 publications that list gene variants that are associated with a certain autoimmune disease. Interestingly, a lot of these genes are located in the same regions on the chromosomes, the so called susceptibility regions. This has led to a “common cause hypothesis” of autoimmune disorders. Several organizations and institutes have established programs to investigate this common cause hypothesis. However, defects of one or more of these genes do not cause an autoimmune disease, but only predispose a person for an autoimmune disease.
The factors that trigger an autoimmune disease are still unknown. Studies with monogenetic twins have revealed that genetic influences only account for 25–40% of the disease risk making gene-environment interactions or environmental influences the predominant factors. The environmental influences are very diverse, rendering research in this area extremely difficult. These influences may be toxic substances like mercury in one case and ultraviolet light or even certain nutrients in another. Moreover, several bacteria, viruses, or hormones are among the suspected triggers of autoimmune disorders. The treatment of autoimmune diseases is typically with immunosuppression: medication which decreases the immune response.
Autoimmune Response : Erythema multiform is a rash that appears as an auto-immune response to a predisposing agent: a bacteria, an immunization, an antibiotic (in this case, amoxicillin).