What is an autoantigen?

An autoantigen is best defined as one’s own antigen that stimulates the production of autoantibodies. In the context of immunology, autoantigens are typically normal proteins or molecules found within the body that, under certain circumstances, can trigger an immune response that mistakenly targets the body’s own tissues. This can lead to autoimmune diseases where the immune system attacks healthy cells, mistaking them for foreign invaders.

This concept is crucial in understanding autoimmune disorders, as these disorders arise from the production of autoantibodies against these autoantigens. When the immune system recognizes these self-antigens as threats, it can result in inflammation and tissue damage.

In contrast, recognizing the other options can clarify the specific nature of autoantigens. Foreign antigens derived from pathogens do not fit the definition of autoantigens, as they originate outside the body. Antigens eliciting a histocompatibility response refer to those involved in immune recognition of non-self cells, primarily related to tissue compatibility and organ transplantation, rather than self-recognition. Lastly, antigens present only in genetically different individuals signify non-self antigens, further distinguishing them from autoantigens.