Immunity + Autoimmunity: When the Immune System Loses Tolerance

Author: Megan Jones (Adv.Dip.NutMed, BHsc.NutMed, Adv.Dip.HerbalMed)

The immune system is extraordinarily sophisticated. Every day, it identifies potential threats, coordinates responses to unfamiliar microorganisms and, just as importantly, knows when not to react. A healthy immune system is not simply an active or “strong” immune system. It is a well-regulated one - capable of responding appropriately while recognising the body’s own cells and tissues as belonging there.

Autoimmunity occurs when part of this recognition system breaks down. Instead of maintaining tolerance towards the body’s own tissues, the immune system mistakenly directs an immune response against them. With autoimmune diseases affecting millions of people worldwide - and conditions including multiple sclerosis, rheumatoid arthritis, type 1 diabetes and inflammatory bowel diseases among the better-known examples - understanding the relationship between immunity and autoimmunity can help make sense of what happens when this carefully regulated system loses tolerance.

Key takeaways

1. The immune system must balance responses to potential threats with tolerance towards the body’s own cells and tissues.

2. Autoimmunity occurs when immune tolerance is disrupted and the immune system mistakenly responds to the body’s own structures.

3. Autoimmune diseases are complex and are thought to develop through interactions between genetic susceptibility and environmental influences.

4. Inflammation is a normal part of immune function, but inflammatory processes can become persistent or dysregulated in autoimmune disease.

5. Nutrition cannot prevent or cure autoimmune disease, but adequate nutrition is important for normal immune system function and general health.

What does the immune system actually do?

The immune system is not a single organ. It is an interconnected network of cells, tissues, organs and signalling molecules working together throughout the body. Its role is to recognise potential threats, coordinate an appropriate response and distinguish between what belongs in the body and what does not. Broadly, immune function involves two interacting systems: innate immunity and adaptive immunity.¹

Innate immunity provides a rapid first response. Physical barriers such as the skin and mucous membranes form part of this system, alongside immune cells capable of recognising common characteristics associated with potentially harmful microorganisms. Adaptive immunity is more specialised. B cells can produce antibodies against particular antigens, while different populations of T cells help coordinate immune activity or identify and respond to affected cells. Adaptive immunity can also develop immunological memory, allowing the immune system to recognise and respond to something it has encountered previously. But identifying potential threats is only part of effective immune function. The immune system must also know when not to respond.

Immune tolerance: knowing what belongs

One of the most important concepts in immunity is self-tolerance. During their development and throughout life, immune cells are subject to regulatory processes that help prevent inappropriate immune responses against the body’s own cells and tissues.² In other words, a well-functioning immune system is constantly balancing several jobs: recognising, responding, regulating, remembering and tolerating.

This balance allows an immune response to occur when appropriate without continuously reacting against harmless substances or the body itself. When mechanisms responsible for self-tolerance break down, immune cells that recognise the body’s own components may escape normal regulatory control. This loss of tolerance is central to autoimmunity.

What is autoimmunity?

Autoimmunity describes an immune response directed against the body’s own cells, tissues or molecules. An autoimmune disease can develop when this immune activity contributes to tissue damage or changes in normal physiological function and results in a recognisable clinical condition.²

Different autoimmune diseases affect different parts of the body. In rheumatoid arthritis, immune-mediated inflammation primarily affects the joints. In type 1 diabetes, immune cells target insulin-producing pancreatic beta cells. In multiple sclerosis, immune-mediated processes affect structures within the central nervous system. Despite their very different presentations, these conditions share an important underlying feature: the immune system is responding to something it would ordinarily be expected to tolerate. This is why describing autoimmunity as simply having an “overactive” immune system does not tell the whole story. It is more accurately understood as a disruption of immune tolerance and regulation.

What causes autoimmune disease?

There is no single cause of autoimmune disease. Instead, research points towards a complex interaction between genetic susceptibility, immune regulation and environmental influences.³ Certain genetic variations can increase susceptibility to particular autoimmune conditions, but genetics alone generally do not explain why disease develops.

Researchers are therefore also investigating a wide range of environmental and lifestyle factors. Depending on the autoimmune condition, these can include:

• certain infections
• smoking
• dietary patterns
• vitamin D status
• certain medications
• hormonal influences
• obesity and metabolic factors
• environmental exposures
• changes in the gut microbiome.³⁻⁵

Importantly, an association between a factor and autoimmune disease does not necessarily mean that factor directly causes it. The bigger question researchers are trying to answer is why immune tolerance is maintained in some people but disrupted in others - and why people with different genetic backgrounds may respond differently to environmental exposures.

Where does inflammation fit in?

Inflammation is often discussed as though it is inherently negative, but it is actually an essential part of normal immune function. When the immune system detects tissue injury, infection or another potential threat, inflammatory signalling helps recruit immune cells and coordinate the body’s response. Under normal circumstances, this process is controlled and temporary, with regulatory mechanisms helping bring the response back towards balance once the immediate challenge has been addressed.

In autoimmune disease, however, immune activity may repeatedly or persistently target particular tissues. Depending on the condition, this can contribute to ongoing inflammatory processes, tissue damage and changes in normal function. So, inflammation itself is not something the body simply needs to eliminate. Regulation is what matters.

The gut & immune system

The gastrointestinal tract has an unusually complex relationship with the immune system. Every day, the gut encounters food components, microorganisms and compounds from the external environment. The immune system must continually determine which substances can be tolerated and which require a response. The gut microbiome - the community of microorganisms living within the gastrointestinal tract - is also involved in extensive communication with immune cells and the intestinal environment. Research is increasingly examining how these interactions may influence immune development, tolerance and inflammatory signalling.⁵

Differences in gut microbial composition have been observed in several autoimmune diseases, although the relationship is complex and research is still developing. There is no single “ideal” microbiome associated with immunity, nor does current evidence suggest that changing the microbiome alone can prevent or treat autoimmune disease. What this growing area of research does highlight is the close relationship between the gastrointestinal environment and normal immune function.

Food, molecular mimicry + autoimmunity

Another area being investigated in autoimmune research is molecular mimicry. Molecular mimicry occurs when molecules from an external source share structural similarities with molecules found within human tissues. Under particular circumstances, an immune response initially directed towards an external antigen may cross-react with structurally similar components of the body.⁶ The concept has been investigated in relation to infections, dietary antigens and the development of autoimmune responses.

However, this does not mean that particular foods universally trigger autoimmunity. Food-related immune responses are highly specific to the individual and the condition. Coeliac disease, for example, has a well-established relationship with gluten. This does not mean that removing gluten (or any other particular food) is appropriate for every person living with an autoimmune condition. Unnecessary dietary restriction can also make it more difficult to achieve adequate nutrient intake. Rather than viewing food through the lens of universal “triggers”, dietary changes in the context of diagnosed autoimmune disease are best considered individually and, where appropriate, with guidance from a qualified healthcare professional.

Nutrition & normal immune function

Nutrition cannot prevent or cure autoimmune disease. What nutrition does provide is something much more fundamental: the nutrients required for normal physiological function - including normal function of the immune system. Immune cells continually divide, communicate and produce proteins and signalling molecules. These processes rely on adequate energy, amino acids, vitamins, minerals and other dietary components.

Several micronutrients have established roles in normal immune system function, including vitamins A, B6, B12, C and D, folate, iron, selenium and zinc. Rather than focusing on individual “immune-boosting” foods or nutrients, a more useful approach is to consider overall dietary adequacy and diversity. A varied diet may include vegetables and fruit, legumes, wholegrains, nuts and seeds, quality dietary protein, sources of essential fatty acids and a broad variety of plant foods providing fibre and naturally occurring plant compounds.

For people living with autoimmune conditions, nutritional requirements may also be influenced by the condition itself, medications, appetite, gastrointestinal symptoms or medically necessary dietary exclusions. This is one reason individual nutritional advice can be particularly valuable.

What about nutritional supplements?

Supplements are not a treatment for autoimmune disease and should not be positioned as one. Their role is much simpler: helping provide nutritional support where dietary intake does not consistently meet requirements.

Nuzest Good Green Vitality, for example, provides a broad range of vitamins and minerals alongside other plant-derived ingredients. It contains nutrients including vitamins A, B6, B12, C and D, folate, iron, selenium and zinc, which contribute to the normal function of the immune system.* The objective is not to “boost” the immune system or alter an autoimmune response. It is to provide daily nutritional support for normal immune function as part of a varied, balanced diet and healthy lifestyle.

Immunity is about balance

“Boosting immunity” has become common wellness language, but the biology of the immune system is much more nuanced. A well-functioning immune system needs to recognise potential threats, respond appropriately, regulate that response, develop memory and maintain tolerance towards the body’s own tissues. Autoimmunity demonstrates what can happen when parts of this finely regulated system no longer behave as intended.

There is still much to learn about why autoimmune diseases develop and how genetics, infections, the microbiome, nutrition and environmental exposures interact. What is clear is that there is no single food, supplement or lifestyle intervention that can prevent or cure autoimmunity. Good nutrition instead plays its most important role where it always has: providing the nutrients required for normal physiological function and supporting the foundations of general health. When it comes to the immune system, normal function is not simply about doing more. It is about knowing when to respond - and when not to.