Cross-Reactivity and Molecular Mimicry in Autoimmune Conditions

• Fatigue
• Achy muscles
• Stiff joints
• Trouble concentrating/brain fog
• Skin rashes

What we ingest and take in from the outside world is HUGE – this creates our adaptive immunity.  Our adaptive immunity is how we react to pathogens in our environment. We are constantly being exposed from the moment we’re born.  

Our gut is often the first point of contact with microbes from the outside world.  Most of which are destroyed by the harsh environment of the stomach, but a hearty few make it through to the intestines.  

The intestines are lined with finger-like projections, called villi, whose primary function is the absorption of nutrients.  These structures along with underlying tissues host the body’s largest population of immune cells. At the base of the villi are the lumen’s tight junctions that prevent the passage of big proteins into the bloodstream.  When you have intestinal permeability, or “leaky gut,” proteins get through, enter your bloodstream, and your immune system either recognizes them or marks them as foreign invaders.

Your adaptive immune system makes antibodies designed to target the bad guys (called antigens) that your immune system has decided will likely harm you.   

Unfortunately, your immune recognition system isn’t perfect.  As long as a molecule’s structure is similar enough to a pathogen already marked as bad or harmful to you, from previous exposure, your immune system registers it as an invader and attacks.  This happens commonly with food that we eat.

Let’s take the example of gluten as it is a common offender.  Gluten is a polypeptide – poly means several, peptide means protein.  So, gluten is made up of several proteins. Proteins are then made up of short amino acid sequences.  These short sequences are what your immune system reads and responds to. If you are sensitive to gluten, your body launches an attack against it every time it’s ingested.  

The tricky part is, the antibodies sent out from your immune system can wrongly tag other proteins as gluten if they have similar enough structures.   For example, casein, the protein found in dairy, looks extremely similar to gliadin, the protein found in gluten; this is an example of cross reactivity.  Other foods that cross-react with gluten include yeast, oats, millet, rice and corn.

Once gluten gets tagged as an antigen (as it is in anyone with gluten sensitivity), your adaptive immune system makes antibodies to seek it out and sound the alarm every time you ingest it.  If you’re eating these other foods that have similar structures to gluten, your body can mistakenly recognize them as gluten and launch an immune response

This process of cross-reactivity is also the same concept as molecular mimicry.  In both cases your immune system confuses food sources as invaders and begins to destroy them.  However, in the process of molecular mimicry, tissues in your body, such as your thyroid, are mistaken by the immune system as foreign.  This happens because some of your major organs have similar AA sequences to food.

Gluten, for example, has very similar amino acid sequences to thyroid tissue and cerebellar tissue.  Because of this, your body can mistakenly attack your thyroid tissue or cerebellar tissue every time you ingest gluten or foods that cross-react with gluten.  This is autoimmunity. Your immune system can’t differentiate your thyroid or cerebellar tissue from the proteins found in gluten due to molecular mimicry.

This is why food sensitivity testing is so important if you’re having a number of unexplainable symptoms.  Reacting to foods can trigger an immune response – that’s really just the basis of it. If you have a leaky gut, you are way more likely to be reactive to foods than other people on top of it.  So the likelihood of beginning the autoimmune cascade is a lot stronger.

Cross reactivity may also explain why some patients don’t recover after going on a gluten free diet.  It’s because the other foods that they’re eating are cross-reactive and your body is recognizes them as gluten.  There are food sensitivity panels available that check for cross-reactivity as an option, as well.

These are two mechanisms that explains how autoimmunity can spiral out of control.  The physicians at HHW can help unravel what’s going on in your body. If you have any questions, make an appointment today!