Published December 2 2013
Secretory Immunoglobulin A (Secretory IgA, or SIgA) is important in protecting the mucosal surfaces of the body. The mucosal surfaces are the first line of protection, as they play a role in defending the body against pathogenic molecules. Secretory IgA is produced by the B-cells of the immune system, which in turn forms immune complexes with the pathogens. If someone has high or low secretory IgA levels, then this not only is a sign of compromised immunity, but it usually is a sign of gastrointestinal problems.
What I’d like to do is expand on the role of secretory IgA so that you hopefully will have a better idea as to how important it is for the optimal health of the immune system and the gut.
Secretory IgA and Immunity. As I mentioned earlier, SIgA is important in protecting the mucosal surfaces of the body. It is specifically involved in “immune exclusion”, which refers to the ability of SIgA to prevent microbial pathogens and antigens such as toxins from gaining access to the intestinal epithelium (1) . This has been demonstrated against the pathogenic organism Shigella flexneri, as it has been shown that SIgA helps to dampen the proinflammatory properties of this organism (2) . So a depressed secretory IgA is a good indication of a compromised immune system.
Secretory IgA and the Gut. You already know that SIgA can protect the cells of the intestine from toxins, viruses, and pathogenic bacteria. As a result, of someone has depressed levels of SIgA, then one will have less protection against toxins and pathogens. As a result, damage to the intestinal lining is more likely to occur. This in turn can lead to an increase in intestinal permeability, also known as a leaky gut.
What Causes An Imbalance In Secretory IgA?
There are numerous factors which can cause a depressed secretory IgA level. Stress is a big factor, which is why the SIgA is tested for on the Adrenal Stress Index panel. Numerous studies show a relationship between secretory IgA and stress (3)  (4) . One of these studies did a comparison between nurses working in emergency wards and hospital clerks. And the study found that the nurses, who not surprisingly had higher levels of stress, had SIgA levels which were much lower than that of the clerks (3) . Other factors which could lead to depressed SIgA levels include poor nutrition, certain viral infections (i.e. EBV) and other pathogenic bacteria, and even certain medications, such as NSAIDs.
Based on these factors it shouldn’t be a surprise as to why many people have depressed secretory IgA levels. Many people deal with prolonged, chronic stress, which is one of the main factors which affects the secretory IgA levels. And many people eat poorly. These two factors alone account for most of the low levels I see in practice. However, some of the other factors I mentioned can cause or contribute to depressed SIgA levels.
How To Test The Secretory IgA levels
There are a few different methods of accurately testing the secretory IgA levels. I usually test this through the saliva. I personally use the company Diagnos-Techs, as their Adrenal Stress Index panel not only tests for the cortisol levels throughout the day, along with the DHEA, but it also tests for the secretory IgA (they call it Total Salivary IgA). Other companies offer similar testing.
Can Depressed Secretory IgA Cause Graves’ Disease or Hashimoto’s Thyroiditis?
There is some evidence that compromised mucosal immunity can lead to infectious, inflammatory, autoimmune, and neoplastic diseases (5) . In past articles and posts I’ve discussed how problems with intestinal permeability can trigger an autoimmune response. So if someone has a depressed secretory IgA, this can lead to an increase in intestinal permeability. And this in turn can potentially trigger an autoimmune response, thus leading to an autoimmune hyperthyroid condition such as Graves’ Disease, or an autoimmune hypothyroid condition such as Hashimoto’s Thyroiditis.
My practice focuses on thyroid and autoimmune thyroid conditions, and I test the secretory IgA in most of my patients. And just about everyone has depressed levels. Some people have mildly depressed levels, while others have levels that are extremely depressed. When the depressed levels are moderate to severe then this usually correlates with a leaky gut due to the mechanisms I described before. However, there are other tests which will specifically determine if someone has a leaky gut, such as the Lactulose Mannitol test, and the Intestinal Antigenic Permeability Screen by Cyrex Labs, which is the test I prefer to use.
Retesting The Secretory IgA
I often get asked by patients and non-patients how I determine if someone’s immune system health has been restored. Well, one of the ways is by retesting the secretory IgA levels. Since most of my patients have depressed secretory IgA levels, the obvious goal is to get these levels to within the normal reference range, which usually is a good indicator of a healthy immune system and gut. For someone who has extremely depressed levels it can take a good amount of time to get these within the normal reference range. But once this happens the person usually has experienced a dramatic improvement in their condition, and many people will be completely free of symptoms at this point, and often times the serum tests will look great as well.
Secretory IgA levels can be elevated. This frequently is indicative of an infection, although other factors can cause this as well.
Some people have a systemic deficit in capacity to produce secretory IgA, which is an inherited problem. If someone initially presents with a depressed SIgA, follows a natural treatment protocol to restore the health of their gut and immune system, and the SIgA fails to increase on a retest, then this could indicate a genetic problem. The way to confirm this is to have the person do a serum IgA test and to see if this is depressed as well.
So hopefully you now have a better understanding as to how important secretory IgA is to our health. Although SIgA doesn’t relate directly to thyroid health, since it plays an important role in immunity, as well as gut health, depressed SIgA levels can make someone more susceptible to having a leaky gut. This in turn can trigger an autoimmune response, thus leading to an autoimmune thyroid condition such as Graves’ Disease or Hashimoto’s Thyroiditis. As a result, if someone has depressed SIgA levels then the obvious goal should be to put them on a natural protocol to help restore the health of their gut and immune system.