The Ebola virus: still quite deadly and able
to avoid detection by human immune system-
the most advanced and complex on Earth.
|The lymphatic system in most animal species is the most important physiological system of combating foreign bodies such as viruses, bacteria, or fungi. The lymphatic system varies from animal to animal, but in humans, it consists macroscopically of: The bone marrow, spleen, thymus gland, lymph nodes, tonsils, appendix, and a few other organs. However, the functioning of the lymphatic system is most easily seen at the microscopic level where the white blood cell is the single most important element. White blood cells are produced, as are red blood cells, in the marrow of human bone. When mature, white blood cells actively seek out possible pathogens or any other unknown substance and, using a very complex chemical signaling system, can attack directly or provide for the removal of this substance. For example, if a white blood cell is alerted to the presence of unwanted bacteria in the blood, it will find this bacteria and surround it as an amoeba does with food. After the white blood cell (or T cell) has the bacteria trapped, it releases a deadly toxin that destroys the bacteria by breaking its outer membrane.||The wastes of this type of killing can show up, if in enough numbers, as pus or other eruptions on the skin. The lymphatic system and immune system consist of millions of different particles vital to the identification of unwanted materials in the body. Antibodies, antigens, and B cells are each very important chemical identification of these intruders. The body is able to learn, with these molecules, to combat viruses or bacteria, for example, that it has encountered before by chemical "remembering" what the external molecular structure looks like. This system of antigens and antibodies allow people to be immune to diseases if they have encountered them previously. Thus, most harmful bacteria and viruses in people are ones that are not easily identified as harmful by the immune system. After the disease has run its course, the immune system learns the identity of this pathogen and can respond quickly to the threat the next time the foreign body invades.|
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