Autoimmunity results from a lack of immune system regulation or disturbance of immunological tolerance. The mechanisms involved in autoimmune disease are quite complex and still being understood today. It is important to understand that genetics, diet, lifestyle and some medications can play a role in the initiation of autoimmunity via various mechanisms.

Our immune systems ultimate goal is to protect our bodies from pathogens such as viruses, bacteria, allergens and toxins. When such pathogens enter the body, the immunes system sends out T cells in defence that target antigens contained in these pathogens.

Normally, antibodies to these antigens are released by the immune system enabling their destruction in order to protect the body. However, in autoimmune disease the immune system produces autoantibodies, immune proteins, that are unable to distinguish between ‘self’ from ‘non-self’ and go on to attack healthy cells (Hosseini et al. 2015).        

For example, in Rheumatoid arthritis (RA), autoreactive T cells attack the joints. In Inflammatory Bowel Diseases (IBDs) such as Crohn’s Disease and Ulcerative colitis autoreactive T cells attack certain areas in the digestive tract. More specifically in Crohn’s they attack multiple regions of the entire gastrointestinal tract, whereas in Ulcerative colitis they attack the large intestine or colon.

References:

Hosseini, A.M. Majidi, J. Baradaran, B. & Yousefi, M. (2015). Toll-Like Receptors in the Pathogenesis of Autoimmune Diseases. Adv Pharm Bull. 5 (Suppl 1): 605-614. Doi: 10.15171/apb.2015.082.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4708030/pdf/apb-5-605.pdf