do cells of the immune system go awry or? | Coursera Community
Coursera Header

do cells of the immune system go awry or?

  • 4 August 2019
  • 2 replies

Badge +1
I have read that autoimmunity happens when the immune system overreacts to a pathogen (see General Pathophysiology). But I think the immune system is doing what it is designed to do. It tries to communicate with the cell to see if it is “self” but the cannot respond for some reason. One hypothesis is that our cells get coated with toxins that the body cannot dispose of. That somehow block it’s ability to respond . With age and loss of hormones some woman like myself get diagnosed with primary biliary cirrhosis or it is now called something else. Somehow estrogen protects. I wonder if there is a way to understand what is going on when autoimmunity is triggered.

2 replies

I am a junior resident in internal medicine and by no means an expert on the topic. However, I will gladly share what I do know about this.

Autoimmunity is a highly complex topic. In simplest terms, it is the failure of your immune system to differentiate between self and non-self antigens. Like most other complex disorders it is considered multi-factorial. In other words, it stems from the intricate play between genetics and the environment.
If a patient has a family history of autoimmune disease, they are generally at a higher risk of developing an autoimmune disease as well compared to the general population (not necessarily the same type of autoimmune disease, mind you). Twin studies have confirmed this as well. However, twin studies have also shown that if an identical twin has an autoimmune disorder, the co-twin will not always have it as well even though they share 100% of their genetic material. This implicates environmental exposure in the pathogenesis of autoimmune disease.

A very fascinating trend to note is that autoimmune diseases have a higher incidence in developed countries and a lower incidence in developing countries where infectious disease incidence is higher!
the "Hygiene Hypothesis" was put forth to account for this discrepancy. In essence, early childhood exposure to pathogens plays a key role in "training" our immune system to become more competent and less likely to confuse self antigens with pathogenic antigens.

On the other hand, there are diseases where exposure to a specific pathogen CAUSES rather than than prevent autoimmune disease. Rheumatic Heart Disease is a prominent example of this phenomenon. it happens in some people who contract rheumatic fever (sore throat from a strep bacteria) sometime in their childhood. Basically, a child gets rheumatic fever and their immune system produces antibodies to fight off the bacteria. However, in a small percentage of cases, and owing to genetic variation, some people may have self antigens that resemble the antigens found on the bacteria. This is known as molecular mimicry. As a result, other tissues in the body, specifically the heart valves (the mitral valve in most cases) get caught in the crossfire and are damaged by the same antibodies that were supposed to help you fight off the strep infection. This results in rheumatic heart disease later in life.

So you see, autoimmune disorders truly are a complex family of disorders where exposure to pathogens may play a role in both protecting against AND causing these conditions in genetically predisposed individuals.
Badge +1
Hi Chess,
thanks for going into so much detail in your response. It is good to know how modern medicine explains this phenomenon. Of particular interest to me is how popular gene theory has become. I think it is somewhat common knowledge that genes can turn off or on due to environmental factors. My mother had scarlet fever and her father had Bright’s disease. She lived a very healthy life except for smoking which cut it short I believe. Their environment was more conducive to life I believe. I don’t believe that this topic can be understood using current concepts actually. I think the future holds the answer. I do believe that thoughts influence the body and that our immune system works best when we don’t mess with it too much. Our bodies evolved for a very long time whereas our attempts to intervene are very minuscule on the scale. Keep up the good work! Pray for your patients and don’t be afraid to not know.