Why the Immune System Can Attack the Body

Why this matters

Being told the immune system is attacking the body can feel alarming and difficult to make sense of. Understanding the mechanisms involved replaces that alarm with a clearer picture of what’s actually happening and why.

How the immune system normally avoids this

The immune system uses a process called self-tolerance to distinguish the body's own cells from foreign ones. During early immune development, cells that react too strongly to the body's own tissue are eliminated or suppressed. Regulatory T cells also actively prevent immune responses from turning against healthy tissue. This system works well most of the time, but it isn’t perfect.

Why it sometimes goes wrong

Several mechanisms can disrupt self-tolerance. Molecular mimicry is one of the most studied. When an infection occurs, the immune system learns to recognise the pathogen. If part of that pathogen closely resembles a protein found in the body's own tissue, the immune response can accidentally begin targeting that tissue too, even after the infection has cleared.

Genetic factors also play a role. Certain gene variants affect how well the immune system distinguishes self from non-self, or how effectively regulatory mechanisms suppress inappropriate responses. These variants don’t guarantee autoimmune disease but significantly increase susceptibility.

Hormonal influences matter too. Autoimmune conditions are significantly more common in women, and hormonal changes associated with puberty, pregnancy, and menopause all appear to influence immune regulation in ways that aren’t yet fully understood.

What this produces

When self-tolerance breaks down, the immune system produces autoantibodies, immune proteins that specifically target the body's own tissue. Different autoantibodies target different tissues, which is why autoimmune conditions present so differently from one another. The presence of specific autoantibodies in blood tests is often how autoimmune activity is detected and monitored.

What you could do

When specific antibody tests are mentioned in clinical conversations, these are testing for the presence of autoantibodies that indicate the immune system is responding to particular tissues

• Understanding that this process develops gradually, and can be present before symptoms appear, helps contextualise why monitoring continues even during stable periods

This article is for general information purposes only and doesn’t constitute legal, financial or benefits advice. For advice specific to your situation, please speak to a qualified professional or contact an organisation such as Citizens Advice, who may be able to assist you further.

References:

‘Mechanisms of human autoimmunity’ (2015) https://doi.org/10.1172/JCI78088

‘Molecular mimicry and immune-mediated diseases’ (1998) https://doi.org/10.1096/fasebj.12.13.1255

‘Women and autoimmune diseases’ (2004) https://doi.org/10.3201/eid1011.040367