Understanding Antibodies: IgA
This is part 3 of 4 of our Understanding Antibodies segment. See our previous blog posts on IgM and IgG antibodies if you are just catching up before we dive into IgA antibodies!
Immune System Scouts
Unlike IgM and IgG antibodies, IgA antibodies are the antibodies that reside primarily in mucous membranes and secretions. This is crazy important, because mucous membranes and secretions are what lines most of our barrier with the outside world. Places like our mouth, nose and intestines. Essentially anywhere that our internal body meets the external world, IgA is there. They are like the scouts of the immune system.
Having scouts are important when you are trying to fend off enemies. Similar to the cells in the innate immune system that are the first responders, IgA antibodies can respond quickly to threats. They are good at fighting bacteria and yeast. They are also good at helping to produce other antibodies like IgG.
But apart from things like bacteria, IgA antibodies can also react to things in our environment. Food is one of those things that is often triggering to IgA. If IgA antibodies respond to big proteins like gluten, it can lead to conditions like celiac.
Types of Antibodies: IgA
IgA antibodies are the main antibodies found in our secretions. They represent approximately 15% of all antibodies in the blood, but more than 80% in our bodily fluids. These include things like our tears, lungs, sweat, saliva, breast milk and intestinal mucus. (Yes, there is A LOT of mucus in the gut). And they mostly communicate with the outside world to determine what are considered outsiders.
Because our mucus secretions are mostly on the borders of our body, these antibodies speak with a lot of things that are not “us.” If we were to stick with my Umbrella Academy reference, IgA’s would be considered the Number 4 of the family. (You know, the one with telekinesis – that can communicate with multiple planes of existence!?)
Because IgA antibodies have so much contact with the outside world, they are especially good at identifying and blocking bacteria from getting in. They can create a sort of barrier for our body to slow down or reduce transportation of the bacteria into our bodies. Therefore it is an incredible protection in the sensitive parts of our bodies like our eyes, ears, nose, mouth and intestines.
Clinical Relevance of IgA
IgA antibodies can be very helpful for indicating infection. Measurements of IgA antibodies against bacteria and other organisms can indicate if we have infections or immune system responses in those areas.
For COVID-19, IgA antibodies can be tested. Since the coronavirus likes to hang out in the back of our nose and throat, IgA antibodies can be produced to help fight it. Or at least to help block it’s passage into our bodies. Our hope is that if our bodies can produce enough IgA response, it will prevent COVID-19 symptoms in other places like our blood vessels.
But measuring IgA antibodies in the blood is not always reliable. Since IgA antibodies are mostly in our secretions, true blood measures may not be as accurate. Getting samples from our mucus secretions or from our fecal matter may be a more reliable marker for measuring these types of antibodies in our body. Something that is not always pleasant to do.
IgA antibodies are incredibly important for autoimmune diseases. IgA antibodies are directly produced in several conditions like celiac disease and IgA nephropathy. But IgA antibodies are also produced often when there is inflammation in the intestines. And IgA antibodies can be linked to IgG antibody production in the body. So some responses to bacteria in our intestines may help to stimulate some autoimmune diseases.
IgA antibodies are easy to measure in the blood stream and in fecal matter. If you are interested in getting COVID-19 IgA testing or antibodies tested for certain diseases, talk to your doctor. We also offer many different types of antibody testing in our office as well. Next, we will go through IgE antibodies
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