The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. Immune systems appear even in the most structurally-simple forms of life, with bacteria using a unique defense mechanism, called the restriction modification system to protect themselves from viral pathogens, called bacteriophages. Immune system disorders occur when the immune response is inappropriate, excessive, or lacking. Fortunately for most of us, the immune system is constantly on call to do battle with bugs that could put us out of commission.
The immune system has a series of dual natures, the most important of which is self/non-self recognition. Each cell in our body has an antigen that tells the immune system that it is part of us and should not be eliminated. It is through antigens that the immune system knows which cells to attack and which to leave alone. Sometimes the process breaks down and the immunesystem attacks self-cells. This is the case of autoimmune diseases like multiple sclerosis, systemic lupus erythematosus, and some forms of arthritis and diabetes.
The innate immune system is the dominant system of host defense in most organisms. The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. This means that the cells of the innate system recognize, and respond to, pathogens in a generic way, but unlike the adaptive immune system, it does not confer long-lasting or protective immunity to the host. Innate immune defenses are non-specific, meaning these systems respond to pathogens in a generic way. Natural killer cells, or NK cells, are a component of the innate immune system.
Both innate and adaptive immunity depend on the ability of the immune system to distinguish between self and non-self molecules. Helper T cells regulate both the innate and adaptive immune responses and help determine which types of immune responses the body will make to a particular pathogen. Adaptive immune responses are actually reactions of the immune system to structures on the surface of the invading organism called antigens. The immune system is enhanced by sleep and rest, and is impaired by stress.
One of the drawbacks of chemotherapy treatment for cancer, for example, is that it not only attacks cancer cells, but other fast-growing, healthy cells, including those found in the bone marrow and other parts of the immune system. In cancer cells, genetic changes cause changes in the cell-surface antigens such that the person's immune system (hopefully) no longer recognizes them as "self" and destroys them. Boosting the immune system has been shown to be therapeutically valuable in treating a wide variety of cancers, chronic viral infections and other illnesses. Some cells of the immune system can recognize cancer cells as abnormal and kill them. But some new treatments aim to use the immune system to fight cancer.
Another important role of the immune system is to identify and eliminate tumors. To the immune system, these antigens appear foreign, and their presence causes immune cells to attack the transformed tumor cells. The main response of the immune system to tumors is to destroy the abnormal cells using killer T cells, sometimes with the assistance of helper T cells. Clearly, some tumors evade the immune system and go on to become cancers. However, if the immune system is stressed and not functioning properly, a cancer cell may multiply before the immune system has a chance to kill it.
The immune system is complex, intricate and interesting. Protect the immune system and you will live a long healthy life. To understand the power of the immune system, all that you have to do is look at what happens to anything once it dies. That sounds gross, but it does show you something very important about your immune system. Although the immune system is extremely complex, its basic strategy is simple: to recognize the enemy, mobilize forces, and attack. Your immune system is under assault from herbicides, pesticides and food additives, and also from the immense amount of radiation that is part of our everyday life today. Protect the immune system and you will live a long healthy life.