There are tens, hundreds, thousands of pathologies and issues that can affect the human body.
Insidious viruses waiting in any hideout for the moment to enter your body. Opportunistic bacteria that do nothing until your defenses are low and they take advantage. Mutations caused by different factors that cause problems in cellular function. Although unlikely, even being attacked by a cow is a possibility.
However, despite this vast list, there is one category that is worse than all the others: autoimmune diseases.
Attacked by those who have sworn to protect you.
What are autoimmune diseases, and what factors do they have?
An autoimmune disease is a pathology caused by the improper response of the person’s immune system.
The main cause is that the immune system mistakes a normal component of the body for something foreign and tries to eliminate it. An example would be Hashimoto’s thyroiditis, where the immune system reacts against the thyroid gland.
Fun fact: this pathology causes hypothyroidism by damaging the thyroid gland. But there is another autoimmune disease, Graves’ disease, which causes exactly the opposite, hyperthyroidism. The antibodies generated by the immune system bind to some receptors of the gland and stimulate excessive hormone production.
It’s not always this simple and direct. In celiac disease, also considered an autoimmune pathology, the reaction is against gluten. Gluten is the compound detected as foreign. However, the immune system initiates a response where the intestinal cells are also attacked.
It is estimated that there are approximately 80 known autoimmune diseases, and another 100 that have not yet been discovered.
Almost any part of the human body can suffer an immune attack.
It is so important that even some organs have immune privilege to avoid this.
mmune privilege is a condition that occurs in some regions of the body, such as the eyes or the brain, where immune system activity is limited or even prevented.
These areas are vital, and abnormal immune system activity could lead to death. Among them are the eyes, the brain, and the testicles.
Without testicles, you won’t die, but evolution places great importance on your ability to reproduce.
The prevalence of autoimmune diseases in modern society is quite high and continues to increase, especially in industrialized countries. It is theorized that the causes responsible for this are:
- Increase in the use of drugs, particularly antibiotics.
- In line with this, low exposure to microorganisms during childhood, which help in the maturation of the immune system.
- Diet, with high consumption of ultra-processed foods.
- High levels of stress.
- More accurate diagnoses. In less advanced countries, many autoimmune diseases may go unnoticed or be confused with other pathologies.
A study in the UK concluded that 10% of the population was affected by some autoimmune disease. They are more prevalent in women.
To name a few examples, rheumatoid arthritis has an incidence of 1% worldwide (we have even discussed rheumatoid arthritis in the blog), and multiple sclerosis affects approximately 2.5 million people worldwide (multiple sclerosis in the blog is also highly recommended reading).
Are autoimmune diseases genetic?
And therefore, are autoimmune diseases hereditary? Their appearance is usually due to a genetic predisposition to suffer from the pathology and a series of environmental factors that trigger it. The vast majority are polygenic and complex diseases.
All the autoimmune diseases we have mentioned so far have a genetic cause.
Which, following the main idea, means that pathologies such as rheumatoid arthritis or celiac disease are also hereditary.
Discovering that there is a genetic predisposition in autoimmune diseases is not something that has required in-depth research. When multiple sclerosis cases started popping up in a family like mushrooms after the rain, doctors suspected something was going on.
Autoimmune diseases are hereditary, meaning the predisposition to the pathology will be inherited. It does not mean that your children will necessarily develop them if one of the parents has it.
Certain genes and their alleles increased the trait of developing these pathologies.
For heredity, a key type of study is based on twins. Returning to multiple sclerosis, in twins, 35% of the time, if one of them developed the disease, the other did too.
However, in fraternal twins, who are genetically different, it only occurred 6% of the time.
As a curiosity, people who have a genetic predisposition to immune diseases seem to have greater resistance to infections, and vice versa.
The genes of autoimmune diseases
There are a number of genes that have been shown to be related to a higher risk of developing an autoimmune disease. These are the genetic factors of autoimmune diseases:
- Genes of the Major Histocompatibility Complex (MHC): This involves a region of chromosome 6, in its short arm, coding for more than 200 genes. It is the area of the human genome with the most variability and is responsible for allowing cells to distinguish self from non-self. Its association with autoimmune diseases goes back to 1967 when it was linked to Hodgkin’s lymphoma. As a whole, it is considered the main genetic risk for autoimmune diseases within the human genome.
- PTPN22 gene: This gene has been linked to autoimmune diseases recently. After the MHC itself, it is considered one of the most relevant genes in the appearance of autoimmune diseases. For example, one of its forms, the SNP rs2476601, is after the MHC the gene that causes the greatest susceptibility to rheumatoid arthritis. Its main activity is to be a negative regulator of the T cell receptor (TCR), inflammation, and the response to viruses. This receptor is indispensable in antigen recognition by the cell, and the PTPN22 gene can limit its activity. It also regulates inflammation and promotes interferon production (an antiviral mechanism). In summary, it participates in both adaptive and innate immune responses.
- IRF5 gene: This gene encodes information for interferon production and the antiviral response. However, in the last decade, it has been found that its influence on inflammatory processes is greater than expected by inducing other pro-inflammatory molecules. It has been found that some forms of this gene increase the risk of systemic lupus erythematosus, and it is hypothesized that it is involved in other similar pathologies.
- STAT4 gene: This is a gene from the STAT family (the name gave it away) that regulates gene expression and is acted upon by multiple cellular molecules. It is a basic mediator of inflammation. It has been found to be involved in rheumatoid arthritis, type 1 diabetes, and even psoriasis.
Genetic testing for autoimmune diseases: Can they detect predisposition?
Although it is not the only factor, there is a strong genetic predisposition to autoimmune diseases.
All autoimmune diseases have a genetic cause involved, regardless of the environmental factors that contributed to their triggering.
This allows genetic tests to predict the risk of developing an autoimmune disease, among the known ones. They approximate predisposition.
We want to emphasize again that these are multifactorial pathologies.
Predisposition is based on the genetic part, but it is impossible to control all the environmental factors interacting with the person.
At least in the part we can analyze best, the genome, excellent work has been done. There are mappings and studies both of genetics and epigenetics to discover the variants that exist in autoimmune diseases.
Thanks to this, we know details such as most of these pathogenic variants are found in non-coding regions (which do not contain information for proteins). Or that many of them are located in key regions for the differentiation and maturation of immune system cells, including their activation in response to stimuli.
Unfortunately, there are many rare autoimmune diseases for which we have little information due to the few recorded cases.
Not to mention all the pathologies we have not yet discovered. Or those that may emerge in the future.
These are the exceptional cases.
To know the predisposition for the more common and likely inherited diseases, the tellmeGen DNA test is perfect.
