The human immune system. Many of us who take or took Biology have a somewhat good understanding of what it is for: protecting the body from infections. It is often referred to as one of biology’s greatest defence mechanisms – attacking viruses, bacteria, pathogens before they can cause harm (kind of sounds like superheroes if you ask me). It is precise, complex, and effectively efficient. Yet in autoimmune diseases, this system makes an immense mistake: the body begins attacking itself.
Through transplants and organ donation, the body can sometimes reject a key part that can help cure or save the body. Why? Autoimmunity occurs when the immune system does not recognise the difference between self and non-self receptors, triggering an immune response against healthy tissues. Instead of targeting foreign invaders negatively affecting the body, immune cells attack the body’s own organs and systems. The consequences are different for varying situations: Through Type 1 diabetes, the pancreas fails to produce insulin, and therefore these insulin producing cells are destroyed; in multiple sclerosis, immune cells attack the protective myelin sheath which surround nerve fibres; while in rheumatoid arthritis, the immune system causes chronic inflammation and damage to joint tissue.
Still, one question stays at the centre of modern immunology: why?
Scientists believe the answer lies in a complex interaction between genetics, the environment, and immune regulation. Certain genes, particularly those that are associated with the human leukocyte antigen (HLA) system, appear to increase susceptibility to autoimmune diseases. However, by having these genes alone is rarely enough. Environmental triggers – such as being exposed to viral infections, smoking, stress, changes in the microbiome – can catalyse pushing the immune system beyond its normal boundaries.
One theory that leads in this sector, involves molecular mimicry. Sometimes, pathogens have molecules that are similar in structure to proteins that are found naturally within the human body. After learning to attack the pathogen, the immune system may mistakenly target healthy tissues that resemble it. Instead of trying to protect the body, the immune system is misdirected instead.
This raises an unsettling possibility that the system designed aiming to protect us and preserve survival, may also make us more vulnerable.
There is another paradox. Autoimmune diseases appear to be increasing globally, particularly in industrialised nations. The hygiene hypothesis is one explanation suggesting that increasingly sterile environments may limit the exposure to microbes early in life, preventing the immune system from being able to develop tolerance to certain microorganisms. In other words, modern comfort may unintentionally inhibit the development the function of our immune system.
The hidden complexity of autoimmunity also challenges the idea of the body as a perfectly coordinated machine. Biology often appears ordered from an external perspective, but beneath this lies constant discussion and negotiation amongst cells communicating, regulating, correcting errors. Autoimmunity reveals what happens when these conversations are interrupted and start to break down.
Research into treatments has advanced significantly, with therapies now aiming not simply to suppress the immune system, but to retrain it. The goal is no longer only preventing damage but restoring the tolerance that has developed over so many centuries, reminding the body once again what belongs to itself.
Perhaps the most intriguing aspect of autoimmunity is the philosophy as much as the biology behind it. Identity, at a cellular level, depends upon recognition – certain characteristics enable us to recognise and name different concepts. The immune system’s critical role is deciding what is self and what is other (should not be there). Autoimmune disease comes about when this distinction becomes blurred.
The anatomy of autoimmunity is therefore more than just a medical condition. It is a reminder that even the body’s most sophisticated systems are shaped by uncertainty and are not always reliable and that survival depends not only on defence, but on knowing what deserves protection.
