The human immune defense system consists of two main components, the innate and adaptive. The innate component is so named because it is a general defense system. It is not specialized or specific but consists of basic defenses such as barriers, guard cells and an alarm system. The adaptive component is also aptly named because it develops or adapts over time as a more specialized and specific response.

Think of the two like this. The innate immune response is the automatic defense mechanism against potential foreign invaders such as bacteria, viruses, molds or parasites. It is analogous to defensive barriers, alarms and guards intended to protect or defend us personally or as a society. Such defensive barriers around our borders or sites of value to us may include protective walls, electric fences, locked doors, security guards and automatic alarm systems. Such systems may include automatic motion activated lighting and alarm systems, and low level security guards. This defense though highly effective for most threats, is not very specific, highly trained or lethal against serious threats. It also can be penetrated or breached easily though it may be linked to an alarm system that can signal for help. Therefore, we need the protection of more highly trained and specific defenses of the adaptive immune response.

With the ability of the innate system to signal for help and the adaptive systems ability to develop over time highly trained and specialized cells and antibodies our body has a better protection against various infections and diseases. In out culture, our adaptive protective system includes specially trained police or military such as SWAT teams, green berets, and the delta force. These forces are mobilized when there is an alarm or request for highly specialized and trained protection or defense. Though they may simply arrest or contain a threat they have the ability to mobilize a lethal force when necessary. However, with this amount of power or force available, innocent bystanders can be injured or killed if there are miscommunications or misidentification of threats or potential invaders. This is how the adaptive immune response works.

Our innate immune defense response is then 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 and neutrophils.

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.

The adaptive response is one that is highly developed and specialized (trained) in humans. It has a memory. When combined with alarm systems from the innate immune system, a rapid, specific, and directed immune response that is also quite powerful can be activated or triggered. However, when such a system is activated, it can also lead to serious collateral damage to the surrounding tissues and cells. If the response bogs down and cannot deactivate itself an ongoing autoimmune condition without an exit strategy can result. This can result in chronic injury to the cells and tissues that is characteristic of what we know as autoimmune disease.

The adaptive response includes the development of specific antibodies or immunoglobulin (IgE, IgM, IgG, IgD, IgA) to infectious agents and proteins the body recognizes as foreign (antigens). Sometimes the body misrecognizes, misinterprets, or mistakes self-proteins or tissues as foreign. When antibodies are made against self-proteins they are called autoantibodies. Examples include antinuclear antibodies (ANA) of lupus and rheumatoid factors or antibodies of rheumatoid arthritis. The result is these classic autoimmune disorders.

The adaptive immune system also includes specialized activated lymphocytes: natural killer T cells, T helper lymphocyte cells, and gamma delta lymphocytes. The latter are also part of innate immune system. Tiny brief lived cell called the plasma cell are also part of the adaptive system. Because the adaptive system has a memory, and is highly trained for future anticipated attacks it can increase its response over time. That makes the adaptive system highly effective in defending us against foreign invaders such as serious infections but also highly dangerous to us if it becomes activated against our own cells or tissues.

The analogies used should help you better understand how our immune system works and how it can fail. It also helps explain how we can develop autoimmune diseases, new abnormal reactions to foreign proteins such as foods resulting in food allergies or sensitivities and how an abnormal gut barrier or leaky gut can be dangerous. Certain good bacteria 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. To learn more about how to maintain a healthy gut, healthy life visit www.thefooddoc.com.

The Food Doc, Dr. Scot Lewey, is an expert medical doctor specializing in digestive diseases and food related illness, especially food allergies, celiac disease and colitis. Dr. Lewey’s is garnering a world wide reputation as the Food Doc. Since completing formal training in internal medicine, pediatrics, and gastroenterology (diseases of the digestive tract), he has over two decades of experience along with his own personal and family experience with gluten and milk sensitivity. He recently founded and launched an educational website www.thefooddoc.com that is nominated for health care site of the year.

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