Table Of Contents

General overview
  The basic cells: Leukocytes
    - B lymphocyte cells
    - T lymphocyte cells
    - Eosinophils
    - Basophils
    - Monocytes
    - Neutrophils
  Fighting off an infection
  Autoimmune diseases

Researchers say, our complex and sophisticated immune system may have made it's very humble beginnings as a virus. Actually, a gene known as a transposon, may have acted like a virus, planting its own genetic material into whatever animals it infected 450 million years ago. This hypothesis helps explain why humans have a second, adaptive immune system. This "jumping gene" made its way into our ancestor's genetic material, and so as humans evolved we developed an immune system which can fight off a wide array of viruses, bacteria and parasites.


Everyday about 6 billion people are exposed to countless types of bacteria, viruses and fungi. Without a method of protection against these and other heath contaminants, human life would cease to exist, as we know it. If you ask the average person why they are healthy, they will probably give you a vague answer. Maybe they'll answer, "Because I eat healthy foods and exercise, " or "because I take care of myself." These answers may account for fitness and wellness in a person, but each has forgotten the key component of healthiness. Almost no one ever acknowledges the real defensive strength of our body, the human immune system. The immune system, although used as a collective term, is not one large organ that protects our bodies. In fact, the human immune system is a cooperation of different types of cells, tissues and enzymes. Each part of the immune system network has it's own specialized tasks and, as a whole, this biological system is one of the most complex known to man. The main function of the immune system is to identify and eliminate all threatening foreign elements from our bodies. Nature has designed our defense system so well that the great majority of free radicals which enter our body are immediately rejected.

There are two types of immunity, innate and acquired. Innate immunity is present even before birth and it mainly based on the immunity of the mother. This includes chemical and physical barriers and specialized cells within the body. Innate immunity fights almost all the foreign particles that threaten the body. Acquired immunity is a more specialized form of immunity, and it is only found in vertebrates. This immunity is the complex result of an encounter, which stimulates an immune response from the body. Acquired immunity involves the use of lymphatic tissues and leukocytes in identifying and destroying threats.

The human immune system runs three main types of aggressive and protective defense responses: the anatomic response, the inflammatory response, and the immune response. The anatomic response is the simplest and is widely taken for granted. This defensive response includes protection by the skin, mucus membranes that line our lungs and stomach acids. The second line of defense is the inflammatory response, which causes increased inflammation and allergic response at the site of entrance. The last and most complex defense is the immune response. The immune response is the key fighter in infections and dangerous situations. Although each level of defense operates differently, each has the same goal, which is to protect our bodies.
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