Secretory IgA and Your Immune Function

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The Pure TheraPro Team

The Pure TheraPro Education Team is comprised of researchers from diverse backgrounds including nutrition, functional medicine, fitness, supplement formulation & food science. All articles have been reviewed for content, accuracy, and compliance by a holistic integrative nutritionist certified by an accredited institution.
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Your mucosal membranes are protected by a slimy gateway that contains compounds with multiple functions. This may sound like something out of a science fiction movie, however, it’s part of our survival mechanism known as our immune system.

Much of your immune function is located in your digestive tract, but it is also found in other mucosal areas in your body—your respiratory tract and even urogenital tract. A bodily substance known as Secretory IgA (SIgA) creates a protective mechanism that guards you from external pathogens and “invaders,” protecting your “ecosystem”.

Secretory IgA is the respiratory and GI tracts’ first line of defense, preventing viruses and pathogens from invading your respiratory system and gut lining, causing possible illness.This is what your immune system is designed to do—protect your system from pathogens. And research proves that when your IgA levels are balanced and working optimally, you are more likely to be shielded from external harms, such as toxins, parasites, viruses, bacteria, yeast and more.

Secretory IgA is like the bar doorman, checking IDs and deciding who can enter and who gets turned away. It’s a technical process known as immune exclusion—limiting microorganisms from crossing the barrier.

Evidence shows that SigA knows the difference between benign and beneficial bacteria as well as pathogenic ones. It also differentiates and protects against environmental toxins, parasites and particulates in food that may cause harm to the system. When your mucosal membranes have enough Secretory IgA, it’s like having 24 hour surveillance security posed to protect you from invaders through this thin, intricate layer of epithelial cells.

Because of its door-bouncing abilities, SIgA works as a first-line director in organizing your microbiome, which plays a huge role in the development and complexity of your immune system. But imagine this “what if” scenario—the doorman gets sick, fired or laid off. He’s drunk, corrupt and disoriented-- and can’t properly do his job. What are the potential impacts on the immune system if SigA isn’t working at 100%?

If a pathogen, toxin or intruder does enter, immune dysfunction might be the result. This may lead to issues such as Leaky Gut Syndrome, Irritable Bowel Disease, a respiratory infection, cold or flu, etc due to the exposure of these invaders to the circulatory system.

Interestingly, those with autoimmune diseases have an imbalance of SigA  levels (can be too high or too low), which makes sense if you think about it. This may have occurred due to genetics, chronic exposure to toxins, infection or parasites or as a result of lifestyle choices—diet, lack of sleep, chronic stress, etc. Certain pharmaceuticals and medications can lower SigA levels and cause an imbalance, affecting your immune system’s differentiation ability. These include anti-inflammatories and antidepressants and many others.

Immune disruption leads to autoimmunity issues when your SigA “doorman” mistakenly allows invaders in, causing immune system confusion. The body begins attacking healthy tissue, such as your thyroid (Hashimoto’s), gut (Crohn’s Disease) or nerves (Multiple Sclerosis), etc.

Even food sensitivities may be the result of  an imbalance in Secretory SigA due to a hyper-vigilance of tagging foods as pathogens and tricking the immune system. It’s a case of confusion and mistaken identity. SIgA imbalance due to chronic stress on the body can cause a cascade effect of systemic inflammation, and further create vulnerability to other invaders—parasites, candida overgrowth and harmful viruses and bacteria.

Keep in mind that Secretory IgA and blood IgA levels are different. Measuring them does not show a relationship to the other. To accurately measure SigA levels, don’t rely solely on blood work. It is best tested through saliva and/or stool samples.

So, how can you naturally balance your Secretory SigA levels?

Vitamin A has been shown to regulate SIgA levels; low levels may be a contributing factor to immune disfunction caused by low SIgA levels. The same appears with zinc deficiency, according to research


Increasing vitamin A levels may also play a role in managing COPD. 

Since Leaky Gut Syndrome can contribute to low SigA levels, it’s important to seal the gut junctures, support the mucosal lining and address possible pathogens that may be causing inflammation and the misfiring of immune response information.



Probiotics are useful tools in increasing SigA levels.

Saccharomyces Boulardii is a probiotic transient yeast that promotes gastrointestinal health by replacing bacteria and yeast invaders, such as candida. When your SigA levels are low, it’s highly likely you also have dysbiosis, or an imbalance of good and bad bacteria in your gut along with the possibility of parasitic organisms.



Saccharomyces Boulardii is a resilient beneficial yeast strain that can survive stomach enzymes, acids, bile salts and influxes in pH levels as well as live at 98.6 degrees. 

Saccharomyces Boulardii has be ability to modulate immunity by increasing SigA in the mucosal lining, hence supporting the immune system as well as regulating gut transit time.

Since Saccharomyces Boulardii is transient, it is also important to replenish the microbiome with probiotics that take permanent gut residence.

Lifestyle changes, such as managing stress, getting enough exercise, eating whole foods help support optimal gut flora and a healthy mucosal lining.

Some foods that re-balance SigA levels include fish oils/cod liver oil, chlorella, bone broth, fermented foods and fiber. 


Our immune systems are powerful security devices created for survival and protection. Support it with knowledge regarding how it works, and focus on natural ways to provide it with the necessary nutrients to do its important job.