Gut Homeostasis

The functioning of the gut is important to our overall health.
Indeed, we now know that intestinal flora plays an important role in health: stimulating the immune system, protecting the host from invading bacteria and viruses, aiding digestion and assimilation of food. Yet, the importance of these bacteria in the gastro-intestinal “GI” tract has been neglected for a long time, while the focus was merely placed on enteric pathogens and other factors leading to gastrointestinal "disorders".Custom Probiotics

Gut microflora is specific to each individual, established at birth- resident flora does not change substantially from birth.   However, many things in life can change the density,numbers/concentration, and ratio of good to bad microflora.  These things include: diet, antibiotics, illness, stress, infection, the list goes on but these are the main effectors.  To achieve homeostasis, there needs to be a balance of good gut flora to bad. "Lactobacilli and Bifidobacteria, should predominate, presenting a barrier to invading organisms. Around 85% of the intestinal microflora in a healthy person should be good bacteria and 15% bad bacteria. The greater the imbalance, the greater the symptoms" Custom probiotics

You'll notice my above links, a fellow FPIES mom shared the link in her search for probiotics for her child.   I typically don't quote websites that are also selling something and proceed with caution with their information (as I just need to re-research it to be sure it is medically sound information) but the above information is good information from their site, which I found easy to read through (although they are selling something and although it looks like a promising probiotic, as always check with the manufacturer for safe ingredients first!).   The reason I have bookmarked their site is because they have a GREAT illustration of the intestines and it's tie to the immune system.  So, if you'd like a look at that- visit this site and scroll down the page a few paragraphs. 

It shows the villi and crypt of the intestines.  The villi and crypt can be damaged in severe/chronic FPIES inflammation, therefore causing further cascading problems of illness from increased intestinal permeability (leaky gut) due to the inflammation opening "holes" in the intestine, thereby causing further damage, deficiencies and mostly allergies/intolerance's as proteins "leak" into the blood stream (via the lymph).   Villi damage can also lead to nutritional deficiencies and weight loss as this is where nutrients are picked up from the broken down food molecules. 

Intestinal flora forms a natural barrier to pathogens and also work together with the GALT (intestinal immune system within the GI tract made of lymphoid cells), comprised of Peyer's Patches (which facilitate the beginning of the immune response in the GI tract), Paneth cells (control microbes) and dendritic cells (micro flora communication).   When the antigenic presenting dendritic cell (where micro flora have their role) activates the lymphocytes,  it leaves the mucousa via the lymph and enters the blood stream via the thoracic duct.  The activated lymphocytes then travel back to the gut and can colonize in the same mucousa or other mucousal sites along the GI tract.    This is where the Tmemory cells are then stored and activated upon re-exposure to trigger (antigen) proteins (and likely why the re-exposure can be a more intense response because of the recognition from previous activated lymphocytes. 

Probiotics can help manage that balance once it has been established (past infancy).   Probiotics have antimicrobial effects (pathogens, toxins), maintain intestinal epithelium (barrier), and regulate the immune system via the GALT (inflammatory responses to allergens and other inflammatory substances). 

It is clear the balance (homeostasis) of micro flora in the gastrointestinal tract is important to immune responses.

Gut Flora and Immune System

One of the roles of gut micro flora is to help regulate the immune system.  Probiotics aren't residential gut flora- they are visitors to help that flora flourish, and even heal a damaged or immature gastrointestinal system. 

We are most familiar with probiotics being responsible for changing the composition (numbers and density) of the resident microflora and thereby restore gut damage but another critical role is in regulation of the immune system. 

"As such, your gastrointestinal tract is lined with its own set of immune cells to help prevent these harmful substances from gaining entry to your body. These immune cells are called the gut-associated lymphoid tissue (GALT). The GALT is the largest mass of immune tissue (lymphoid tissue) in the human body and as such is an important element of the body's immune system. You may be familiar with other lymphoid tissues such as the tonsils and spleen. The tonsils are also located in an area where you are commonly exposed to harmful substances (the throat)."- Allison Tannis, Probiotic Rescue: How You can use Probiotics to Fight Cholesterol, Cancer, Superbugs, Digestive Complaints and More.

Multiple studies have shown Lactobacillus strains promote Th3 (oral tolerance) immune responses.
This article shows that "overall pieces of evidence are beginning to accumulate that support a model whereby disruption of the micobiota also disrupts oral tolerance, potentially by interfering with the dendritic cells (DC) that promote allergen specific regulatory Tcell responses".

The mucosal barrier function of the gut depends on the establishment of of the microflora (at birth). "The immature gut barrier may lead to aberrant antigen transfer and immune responses, thus explaining increased vulnerability to breakdown of oral tolerance....In particular, intestinal colonization acts as an important antigenic stimulus for the maturation of the gut-associated lymphoid tissue. The demonstration that the gut microflora are an important constituent of the intestine's nonimmunologic and immunologic barrier has brought about the concept of probiotic therapy: therapeutic application of consumption of cultures of potentially beneficial bacteria.....Moreover, the intestinal microflora contribute to the processing of food antigens in the gut, and probiotics have been shown to modify the structure of potentially harmful antigens and reduce their immunogenicity in vitro and in vivo, together with a potential to dampen hypersensitivity reactions . These effects are seen as a significant improvement in the clinical course of atopic dermatitis (eczema) in infants given probiotic-supplemented elimination diet, and in parallel, markers of intestinal and systemic allergic inflammation decreased significantly."Functional Foods and Probiotics.

As I read through several articles in my research on the role of probiotics and established micro flora, I come across language that suggests that with impaired immunity regulations, the body isn't just attacking food proteins but the established micro flora as well.   This article on Early Nutrition is an insightful read for this concept. 

Within much of the research is reminders that there is so much more to be researched in the field of microbiota and probiotic therapy (effects and limitations of).   Initial research has shown addition of beneficial strains of lactobacillus and bifida bacteria to be a helpful component in the treatment of inflammatory disorders.