Le système immunitaire - Plus de détails
The term 'immune' comes from the Latin immunis, meaning 'free' which, in the context of the immune system, refers to invading foreign agents. The immune system is our collective army - a billion white blood cells, bone marrow, antibodies, cytokines and the thymus - that identifies and destroys millions of microbes (bacteria, viruses, parasites and fungi) that enter our bodies every day, as well as the thousands of cells that have become genetically abnormal or cancerous. By doing this vital work, our bodies are preserved; without it, we would be dead in a matter of days.
All animals - from the single-celled amoeba to humans - have an immune system. In general, the more complex an organism is, the more complex its immune system is. The human immune system is as complex as our nervous system and can read responses to specific diseases and remember those responses decades later. The memory of the immune system is, of course, the basis of vaccination - the injection of disease toxins into the bloodstream to stimulate an immune response so that, if the disease is contracted later, the immune system is already prepared to fight it.
The human immune system can be divided into two distinct parts that protect us in different ways. The first is natural (or non-specific) immunity and the second is adaptive immunity. The first is a reflex or automatic response system that is programmed at birth to protect us. For example, if we cut ourselves, there is an immediate inflammatory response, followed by a cluster of macrophages that absorb bacteria. This is a non-specific response, and the reaction is the same regardless of the nature of the infection. Another example of non-specific immunity is the activity of natural killer cells. NK cells can automatically destroy cancer cells and virus-infected cells.
The second type of immunity - adaptive immunity - is much more complex and is based on the ability of T and B cells to respond selectively to thousands of different non-self antigens - viruses, bacteria, cells and large protein and polysaccharide molecules. An antigen is, in effect, something that triggers an immune response. This system is able to tailor a response to the specific invader it encounters and remembers that response, so the immune system learns by experience, just as our nervous system learns. Even if we don't have a good memory, our immune system does.
Before our immune system can destroy invaders or cancer cells, it must recognise them. After all, the vast majority of our cells, which are healthy, are not to be worried. In other words, the immune system must be able to detect itself what is foreign to it. In the case of a genetically damaged cell, it must be able to read the signals indicating a problem in the cell.
Recognition therefore plays an essential role in immunity, and this is the most complex problem for the immune system: our body and its cells are constantly changing and we are constantly exposed to new invaders. A delicate balance is required. If the immune system is overactive, we end up attacking our own body, as in the case of autoimmune diseases and allergies. If the immune system is too "lax", invaders cause serious damage to our body and cancers can develop uncontrollably.
Mediation of the immune system
All immune system responses are mediated by white blood cells (leukocytes, including T, B and NK cells, monocytes, phagocytes, basophils, neutrophils and eosinophils), specialised cells in various tissues (macrophages, mast cells) and hormones and other chemical messengers carried by the blood and lymphatic systems. The vast majority of immune system cells originate from bone marrow precursors and circulate in the blood and tissues. For example, T and B cells, which function through the lymphatic system, originate in the bone marrow, but T cells migrate to the thymus where they mature (hence "T cell").
ImunoBran® MGN-3 and the immune system
ImunoBran® MGN-3, a dietary supplement made from rice bran and enzymes from the shiitake mushroom, can significantly increase the activity of weakened immune systems. Although it is still a mystery how it works, it stimulates the production of cytokines, the messenger molecules that control the activity of the immune system.