Autoimmune diseases occur when the body's immune system attacks its own tissues and organs, mistaking them for foreign invaders. Viruses can trigger autoimmune diseases in several ways:
Molecular mimicry: Some viruses have proteins that resemble proteins found in human tissues. When the immune system mounts a response to the virus, it may also attack the body's own tissues that have similar proteins. For example, the Epstein-Barr virus (EBV) has proteins that are similar to those found in thyroid tissue, and infection with EBV has been linked to autoimmune thyroiditis.
Polyclonal activation: Viral infections can stimulate the immune system to produce a large number of antibodies that cross-react with self-antigens. This is known as polyclonal activation, and it can lead to autoimmune disease. For example, infection with the Coxsackie B virus has been linked to the development of type 1 diabetes, possibly due to polyclonal activation of B cells.
Increased antigen presentation: Viral infections can increase the presentation of self-antigens to immune cells, making them more likely to mount an attack on the body's own tissues. For example, infection with the hepatitis C virus has been linked to the development of autoimmune liver disease.
Dysregulation of immune response: Some viruses can dysregulate the immune response, leading to the development of autoimmune disease. For example, the human immunodeficiency virus (HIV) can impair the function of regulatory T cells, which normally prevent autoimmune responses.
It's important to note that not all viral infections lead to autoimmune disease, and not all autoimmune diseases are triggered by viruses. However, viral infections can play a role in the development of some autoimmune diseases.