Sunday, July 15, 2007

Leaky gut and the innate immune system explained

Our innate immune defense response is an automatic and a non-specific system. It consists of the barriers such as the skin and the intact intestinal wall of the digestive tract. The intact intestinal wall is similar to a fence or wall. It is patrolled by certain immune cells that are like security guards or rent-a-cops, guarding the body. This includes white blood cells circulating in the blood or present in the intestinal lining. Circulating white blood cells typically include cells known as neutrophils, eosinophils, and natural killer T lymphocytes. Lining the intestinal wall (skin and respiratory tract) are other white blood cells and immune cells such as basophils, dendritic cells, phagocytes and macrophages. In the intestine white blood cells present in small numbers may be mobilized to the area for specific threats. These include eosinophils, mast cells, lymphocytes and neutrophils. These latter cells are increased in such conditions as eosinophilic esophagitis, eosinophilic colitis, eosphinophilic gastroenteritis, mastocytic enterocolitis, celiac disease, lymphocytic colitis and bacterial infections of the gut such as E. coli associated enterocolitis and other infectious colitis.

The intestinal lining is normally an intact barrier except when signaled to allow some bigger particles through such as certain proteins or other nutrients. The intestinal tract lining has a single layer of cells of the epithelial cell type. These cells are joined tightly, shoulder to shoulder, through a scaffolding of proteins, such as occludens. These tight junctions can open up on signal, from proteins such as zonulin. Certain normal signals permit the opening of the gaps between the lining cells, the paracellular spaces, or decrease the tight junctions resulting in increase intestinal permeability transiently. However, abnormal stimuli can trigger opening of the tight junctions resulting in abnormally increased intestinal permeability or leaky gut. When tight junctions open up wall of the gut may become abnormally permeable or leaky allowing it to be penetrated by foreign proteins including bacteria, viruses, molds, parasites and intact food proteins or lectins. Impairment of gut wall integrity or barrier function is an abnormal innate immune defense. It is like an insecure border, fence or wall.

Various immune cells of the innate response can release chemicals to contain or destroy invaders if they are near the area of an impaired barrier or they recognize that an invader is trying to get through just like a border patrol or roving security guard. Some of the tissue based immune cells destroy the invaders by actually eating them (phagocytes, eating cells and macrophages, large eating cells). They also are able to clean up left over debris and promote healing in a non-specific manner.

Certain good bacteria, such as acidophilus, lactobacillus and bifidobacter, residing in our gut actually help maintain our intestinal wall barrier function, act as antibiotics killing bad bacteria and inhibit other bacteria and yeast from taking over our system. Probiotics containing such bacteria like VSL#3 and Flora Q help promote and maintain a healthy intestine and intact gut wall.

Certain foods, such as gluten can increase gut permeability through the innate immune system. If you have the right genetic pattern (HLA DQ2 or DQ8) an abnormal adaptive immune response can result in serious intestinal injury that defines Celiac disease. However, an abnormal innate immune response can occur non-specifically in anyone resulting in gluten intolerance or sensitivity with all its associated symptoms or illness. Certain bacteria or yeast such as Saccharomyces cerevisiae (Brewer’s or Baker’s yeast, dietary yeast) can trigger an abnormal adaptive immune response in genetically predisposed people resulting in Crohn’s disease or colitis. To learn more about the immune system subscribe to this blog as we explore this further in future postings. Also visit to learn how to achieve and maintain a healthy gut, healthy life.

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