What are probiotics:
Probiotics can be simply described as “good bacteria” that live in all animals (and humans) intestines. Most of us would be surprised to know that for every cell in our body, we have about 10 bacterial cells living in our gut (which in humans makes about 10 trillion bacteria). These bacteria form an integral part of our bodies, and have a wide range of functions – they compete with bad bacteria and maintain gut health, they regulate and stimulate the immune system, aid digestion, break down toxins and allergens, regulate cholesterol uptake, produce essential vitamins, and control inflammation.
Probiotics populate the gut from the moment of birth, and continue to develop during lactation and early development. Typically most animals will form a stable population of probiotics by the time they are weaned. This early development of balanced probiotics is essential for normal immune system development, and there is a lot of evidence that now shows that the development of allergies and asthma in both people and animals can be linked to poor probiotic balance in early development.
Under normal circumstances, these resident gut bacteria cause neither pathogenesis (disease) nor inflammation in the host, but instead contribute to health maintenance, by forming a barrier layer against colonization by pathogens (bad bacteria or other intestinal microbes) and by aiding in nutrient digestion and assimilation. The most important feature of a good probiotic is that it causes no disease, and that it is able to survive the passage through the stomach (in the strong acid environment) and colonise the small, and primarily large intestine.
The most common forms of probiotic are the lactic acid bacteria (eg lactobacillus) , but there are many strains and types, including bacteria, protozoa and yeasts.
How do probiotics affect the immune system:
Probiotics are able to both stimulate and regulate or modulate the immune system, at both a local level (at the gut surface), and remotely in the body.
At a local level, normal contact between probiotic bacteria and gut epithelial cells creates a homeostatic effect, and regulates normal healthy gut function. If imbalance or depletion of these probiotics occur (called intestinal dysbiosis), removal of these routine signals at the gut epithelial surface can lead to a breakdown in these regulatory immune mechanisms and consequently promote aggressive and uncontrolled inflammatory responses – such as is the case in Irritable or Inflammatory bowel disease (or chronic disease like Chrohn’s disease in humans).
On a wider scale, intestinal probiotics can result in stimulatory messages to the gut lymphoid tissue (known as GALT or Peyer’s Patches), which can then further translate into systemic messages sent out via the blood and lymphatics that can affect T cells and antibody production and overall stimulation and enhancement of immune responses. It has been clinically shown that response to vaccination is much more profound, and long lasting, in animals which have healthy levels of probiotics.
In non-disease states, such as in allergies and chronic disease, probiotics have been shown to be able to down-regulate the immune system, reducing the production of inflammatory cytokines, and limiting IgE and histamine release in allergies. There is also some recent evidence that probiotics may have some anti-tumor activity and cancer protective properties.
At the level of the gut, probiotics are also able to enzymatically hydrolyse potential toxins, but more importantly, allergens (reactive substances involved in allergy), thus limiting exposure and uptake into the body. Correcting intestinal dysbiosis also improves epithelial barrier function, thus repelling many allergens from absorption into the body.
There is gathering clinical evidence that certain probiotic strains can be used effectively in neonatal and paediatric care to provide the necessary bacterial signals which, in early life, enable the immune system to develop appropriately and to avoid allergic sensitization. Ensuring that puppies and kittens have correct probiotic populations (either by exposure to appropriate raw food diets, or by probiotic supplementation) may play a critical role going forward in the fight against allergic skin disease.