LivingWhat is an autoimmune disease and why does it...

What is an autoimmune disease and why does it occur?

The immune system is a very complex mechanism involving hundreds of molecules, cells and structures that must be coordinated to perform a given function. Due to the degree of complexity, the regulatory elements are many and varied, but errors do sometimes occur . One type of these failures leads to autoimmune diseases, but how do you get to this point?

What is autoimmunity?

The first time that the concept of autoimmunity appeared in the medical field was at the hands of the German scientist Paul Ehrlich, at the beginning of the year 1900 . This brilliant doctor and researcher identified a series of reactions and gave it the name of horror autotoxicus . However, it would be many years before the mechanism began to be elucidated.

Autoimmune diseases or processes can also be referred to as autoimmunity. Globally, autoimmunity is the set of immune responses directed against cells or elements of the body itself , but also against beneficial microorganisms that coexist in our body.

This situation occurs when cells are created that have a recognition error of their own elements , since they detect a molecule as dangerous that they should not. This recognition problem triggers a proinflammatory reaction that is normally chronic and causes a great deterioration in the quality of life of those who suffer from it.

But how is it possible for our immune system to generate cells that attack our own cells?

The importance of self-tolerance

During the development of white blood cells, there is a mechanism to ensure that there is “variety” among these cells, because they will be responsible for detecting external threats. The more variety there is, the more protected the organism will be against different external dangers .

This process of generating recognition diversity is similar to rolling infinite dice , and each generated cell has a specific roll that it will be able to recognize. However, among the probabilities of the dice, there are also some combinations that are present in our cells .

So what happens if a newly created white blood cell appears with the ability to recognize and kill its own cells? Against this possibility, there is a selection process to identify and eliminate these white blood cells before they spread throughout the body and cause disease.

This process is known as “self-tolerance” and requires the coordination of many molecules and cells of the immune system. As it is already easy to guess, if there is a failure in this process, the cells capable of recognizing their own molecules as dangerous, can spread throughout the body and generate autoimmune diseases .

Can an autoimmune disease be inherited?

Although the exact mechanisms are still half-resolved, it is known to be the result of a combination of several factors . On the one hand, we have a genetic component , when a variant in a gene confers a predisposition to failure of checkpoints .

However, this genetic factor can go unnoticed if the rest of the components compensate it: environmental factors and natural tolerance mechanisms . Among the environmental factors and tolerance mechanisms would be pathogen infections, other diseases, a varied diet with beneficial microbiota, chronic stress or anxiety, and many more.

Therefore, a genetic predisposition can be inherited and depending on the severity of that mutation, it is possible that the disease does not develop or does so to a lesser extent if it is diagnosed early and the necessary measures are taken.

What are autoimmune diseases?

Within the types of autoimmune diseases, they can be classified in a simplified way according to whether they are caused by auto-antibodies (or reactive antibodies), by autoreactive T cells or by both . In both cases, the antibodies or T cells recognize their own antigens (molecules) in different tissues of our body.

There are many types of autoimmune diseases, but among the most common or known would be:

  • Psoriasis
  • Rheumatoid arthritis
  • Graves-Based disease
  • Hashimoto’s thyroiditis
  • Systemic lupus erythematosus
  • Sjogren’s syndrome
  • Chron’s disease
  • Multiple sclerosis
  • Type 1 diabetes mellitus
  • celiac disease

Although not all autoimmune diseases have the same level of severity in terms of the symptoms they cause, they all have a greater or lesser impact on the quality of life of patients . In some cases, it is necessary to proceed with an aggressive intervention and in others, a simple daily treatment may be sufficient.

What is common to all these diseases is that an accurate and timely diagnosis can prevent not only the symptoms, but also the appearance of irreversible effects or a more favorable prognosis within reach. Once diagnosed, can an autoimmune disease be cured?

How is an autoimmune disease cured?

The great variety and complexity of these failures in the immune system is seen in the number of completely different diseases that it causes. This is also reflected in the treatment options that exist, and that must be adjusted to each condition or symptom .

The use of steroids can be of great help in almost all of these diseases, regardless of the process affected. Steroids are compounds that exist in our own body and that, if taken as a medicine, have a generalized anti-inflammatory effect . However, it is not recommended to use them for a long time.

On some occasions, the treatment is simpler, as may be the case with hormone replacement therapy in Hashimoto’s thyroiditis or type 1 diabetes mellitus . With this therapy we provide the hormone that is not produced because the cells in charge are attacked by our body.

On the other hand, we have the opposite case where the treatment consists of the elimination of compounds from the diet , as for celiac disease . If the presence of gluten causes problems because we have antibodies against this molecule, an “easy” option is not to eat it.

However, in severe cases, a bone marrow transplant may be necessary after the cells of the immune system that cause the disease have been eradicated . Even then, it may not be enough to cure the disease. Although this option is usually used in patients with immunodeficiencies or cancer, it is also a possibility for some autoimmune diseases.

Recent studies present bone marrow transplantation as a promising treatment for patients suffering from rheumatoid arthritis or multiple sclerosis . However, more studies are needed in this area to determine which patients would be suitable candidates.

 

References:

Jessop et al. 2019. General information for patients and carers considering haematopoietic stem cell transplantation (HSCT) for severe autoimmune diseases (ADs): A position statement from the EBMT Autoimmune Diseases Working Party (ADWP), the EBMT Nurses Group, the EBMT Patient, Family and Donor Committee and the Joint Accreditation Committee of ISCT and EBMT (JACIE). Bone Marrow Transplant. doi: 10.1038/s41409-019-0430-7

Murphy et al. 2008. Janeway’s immunobiology. New York: Garland Science. 9th edition.

Swart et al. 2017. Haematopoietic stem cell transplantation for autoimmune diseases. Nat Rev Rheumatol. doi: 10.1038/nrrheum.2017.7

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