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The immune system: how does it work?

The immune system consists of a network of cells, tissues, and organs that work together to protect the body from infection. It is the body’s defense against infectious organisms and other invaders, such as viruses, bacteria, fungi, and parasites. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade the body and cause disease. In most cases, the immune system does a great job of keeping people healthy and preventing infections. However, sometimes problems with the immune system can lead to illness.

Overview of the immune system

To function properly, the immune system must distinguish a wide variety of agents, known as pathogens, from the organism’s own healthy tissue. It also needs to be able to distinguish between normal, healthy cells and unhealthy cells by recognizing a variety of “danger” cues expressed by cells that are infected or tumorous. When the immune system first recognizes these signals, it responds to address the problem. If an immune response cannot be activated when there is sufficient need, problems arise, like infection. On the other hand, when an immune response is activated without a real threat or is not turned off once the danger passes, different problems arise, such as allergic reactions and autoimmune disease.

The immune system is complex and pervasive. There are numerous cell types that either circulate throughout the body or reside in a particular tissue. Each cell type plays a unique role, with different ways of recognizing problems, communicating with other cells, and performing their functions.

The immune response: innate and adaptive immunity

An immune response is generally divided into innate and adaptive immunity. Innate immunity occurs immediately through the work of numerous types of circulating immune cells with specialized functions: neutrophils, eosinophils, basophils, mast cells, monocytes, dendritic cells, and macrophages, which recognize general danger patterns through specific receptors called Toll-like receptors (TLRs). Their main feature is the ability to respond quickly and broadly when a problem arises, typically leading to inflammation. However, they cannot distinguish between specific strains of bacteria or viruses.

Adaptive immunity, which is activated by innate immune cells, occurs later, as it relies on the coordination and expansion of specific adaptive immune cells to target specific signals rather than general patterns. Adaptive immune cells, called B and T cells are more specialized and bear unique receptors respectively called B-cell receptors (BCRs) and T-cell receptors (TCRs), with each one able to recognize a specific antigen. An antigen is a molecule derived from the pathogen and processed by the innate immune cells to be presented to adaptive cells in the lymph nodes. The adaptive immune response keeps memory of the pathogen through immune memory cells that are retained for a subsequent use, triggering a more rapid and stronger defense response on the next infection. Because BCRs and TCRs are so specific, adaptive cells may only recognize one strain of a particular pathogen, unlike innate cells, which recognize broad classes of pathogens.

Disorders of the immune system

Complications arise when the immune system does not function properly. They range from simple allergies to genetic disorders that wipe out the presence or function of an entire set of immune cells. We can mention allergic disorders, immunodeficiency disorders, autoimmune disorders and cancers of the immune system.

Allergies are a form of hypersensitivity reaction, typically in response to harmless environmental allergens like pollen or food. Typically there is an overproduction of certain types of antibodies that activates immune cells like basophils and mast cells, which respond by releasing inflammatory chemicals like histamine. Allergic disorders include asthma, eczema, seasonal, food and drug allergies

Immunodeficiencies occur when a part of the immune system is not present or is not working properly. Sometimes a person is born with an immunodeficiency (known as primary immunodeficiency, such as IgA deficiency, severe combined immunodeficiency (SCID), DiGeorge syndrome and Chediak-Higashi syndrome), although symptoms of the disorder might not appear until later in life. Immunodeficiencies also can be acquired through infection or produced by drugs (these are sometimes called secondary or acquired immunodeficiencies such as AIDS).

Autoimmune diseases occur when the body’s own immune system mistakenly attacks its own tissue as foreign matter. Autoimmune diseases include lupus, juvenile rheumatoid arthritis, scleroderma, ankylosing spondylitis and juvenile dermatomyositis.

Some forms of cancer are directly caused by the uncontrolled growth of immune cells. Leukemia is a cancer caused by white blood cells, which is another term for immune cells. Lymphoma is a cancer caused by lymphocytes, which is another term for adaptive B or T cells. Myeloma is a cancer caused by plasma cells, which are mature B cells. Unrestricted growth of any of these cell types causes cancer.

Immune system and diet

Nutrition, physical activity and stress reduction are the three most important areas of action to prevent immune fatigue and to reinforce the immune system. Micronutrient deficiencies or gradual loss of nutrients are known to weaken the immune system, which leads to a general loss of well-being and the deterioration of biochemical reactions in the body. In order to read more about how diet can improve the immune status of elderly people, read our more detailed article on the subject.

However, beyond simply compensating nutrient deficiencies, nutrition can now be used for maintaining or restoring a good functioning of the immune system through a specific modulation of target key genes of immunity. This is the challenge of the nutrigenomic approach. And this is the innovative and unique benefit offered by Actigenomics’product IMMUNITUM®, the first combination of low dose all-natural micronutrients to have been shown to provide prevention against infections, in particular in the case of winter infectious episodes.