The defense system of the body against intruders (pathogens), including microbes, bacteria, viruses, parasites, and fungi, is called the immune system. As the conditions inside the human body are ideal for the growth of many microbes, they try to reside in the human body. The immune system has to terminate them. If the immune system is mistaken and targets the wrong cell, this will reveal havoc of diseases, including allergy, arthritis, AIDS. The immune system is astounding. It remembers many enemies individually; in case of attack, the immune system produces cells, and emissions are released to kill these opponents. The reason behind this durable response is the vibrant, vigorous, and thorough communication linkage.
A considerable number of cells arranges themselves in sets and division of sets, and these cells keep on swimming like a cluster of small fish in the ocean, they transfer information forward and backward. When the alarm is triggered, plenty of psychological changes take place and excretes very potent chemicals. These excretions are entirely in charge of their actions and progression; they team up on their own and assign each other tasks. A hale and hearty immune system are the ones in which the system cells distinguish between its cells referred to as self, and the foreign cells discussed as Non-self. In peace, the immune system and the self-cell remain calm. But once the danger bell rings for the intrusions of microbes, defense mechanism starts, and it unveils the antibodies. The foreign cells could be microbes, viruses, bacteria, fungi, or cells from another organism else than the undistinguishable twin. These cells are known as antigens. Tissue or organ transplant rejection is elaborated here, and the doctors do not go for a transplant when the body considers it as antigen.
Unusual circumstances appear when the immune system evaluates its cells as danger and prepares an attack against the self-cell, considering then Non-self-cell; this phenomenon is Autoimmune disease. Few types of arthritis and diabetes fall into this category. When antigen invades, but it is not harmful, and allergy is the autoimmune response result, then this antigen is an allergen, for example, the ragweed pollen. Lymphoid are the organs of the immune system; that is why it is also known as the lymphatic system. Lymphoid are stationed all over the body, as small white blood cells lymphocytes reside in lymphoid. White blood cells are the integral Pawns of the immune system. The lymphatic system has the lymph vessels to transport the lymph throughout the body, precisely like the circulatory system. The white fluid which travels on the lymphatic vessels which bathes the body cells is lymph. The lymphatic vessels are small vessels that run parallel to the blood vessels. The lymphocytes have the edge of presence all over the body as they travel in blood vessels with blood and lymphatic vessels.