We generally think of the gastrointestinal tract as an organ system devoted to the processing of food and absorption of vital nutrients and water. However, it has other important roles in additon to digestion.
Perhaps the most important to come to light in the past few decades is its central role in defending the body from infection. Protection against illness-causing antigens (toxins, pathogenic bacteria, viruses and foreign substances) is provided by a mechanism known as mucosal immunity (the mucose being the tissue layer that lines the internal surface of the gut). Bacteria within the gut play an important part in mucosal immunity.
Within the gut there are billions of micro-organisms – bacteria, viruses and fungi, known collectively as the gut flora. The most common bacteria, such as Bifidobacterium, Bacteroides, Eubacterium, Fusobacterium, Clostridium and Lactobacillus, are organisms which generally live in harmony with the body and some, particularly bifidobacteria, are linked to significant health benefits.
However, there are also other bacteria, which include species such as the cocci (Enterococcus, Staphylococcus and Streptococcus), the enteric bacteria (E.coli and Salmonella spp.), Clostridium difficile, and the yeast Candida which are pathogenic bacteria and have the potential to cause infection and disease.
In addition, many food components, environmental particles and chemicals pass through the gut, from where they may be able to penetrate into the body and cause disease such as allergy. Gastrointestinal mucosal immunity helps protect the body.
The largest organ of the whole immune system can be found within the walls of the gut, where it is continually exposed to a wide range of antigens.
This organ consists of a unique immune network, known as the Gut Associated Lymphoid Tissue or GALT. The GALT contains large clumps of lymphocytes which attach invading organisms and product antibodies against them. As a result of this activity it has been estimated that the gut controls about 60% of the body’s immune system.
Dr George Tzortzis, Clasado
