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.