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How can infections contribute to autoimmune disease?

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immune system disorder False-color scanning electron micrograph of a T cell infected with HIV (human immunodeficiency virus), the agent that causes AIDS (acquired immunodeficiency syndrome).

Infections can contribute to the development of autoimmune diseases primarily through a mechanism known as cross-reaction (or molecular mimicry).

In this process, an infectious agent produces antigens that are structurally similar to those found on the body's own healthy tissue cells. When the immune system generates antibodies to combat the foreign pathogen, these antibodies may also mistakenly bind to and attack the host's similar "self" antigens. This cross-reactivity can lead to significant tissue damage. For example, the bacteria responsible for rheumatic fever produce antigens that cross-react with heart muscle membranes, while the trypanosomes that cause Chagas disease trigger antibodies that disrupt nerve cells in the bowel.1

Conversely, the hygiene hypothesis suggests that a lack of early childhood exposure to certain microorganisms may also contribute to autoimmune disorders. This theory posits that limited contact with diverse environmental microbes can hinder the proper development of regulatory T cells, which are essential for preventing the immune system from mounting inappropriate responses against the body's own tissues.2