In: Biology
In our discussion of immunology, we defined three lines of defense. Select an example for each line of defense and describe how it functions to defend the body
The human body provides three modes of defence against the entry of the foreign bodies. These are known as the line of defense.
1. The 1st line of defense :- includes mainly the physical and chemical methods of defense against the foreign bodies. It is a type of innate immunity. To enter the body the must break through 1st line of defense. They include usually the skin, mucus, cilia, stomach acid, tears, saliva, sebum, lyzozyme etc.
Skin is the major part of the first line of defense system. It is the largest organ of human body. It provides a protective covering for the entire body. It is water proof in nature thus prevent water borne microbes. Though many microorganisms can stay on the surface of skin but they cannot enter inside the body through the skin.
2. 2nd line of defense :- in any case if the first line of defence is breached the 2nd line of defense comes into action. It is a type of innate immunity. This defense takes place only if foreign body enters the body and is mainly non specific type. Ex WBC and Phagocytes mainly are responsible for such defense.
Ex- macrophages are the cells that move in tissues to check for foreign bodies. On an encounter they engulf the foreign body and carry out lyzozomal activity on the microbes. After digesting the microbe it the leave the tissue.
3. 3rd line of defense :- deals with those antibodies that are unable to be tackled by the 1st and 2nd line of defense. It a type of acquired immunity. Since this line of defense is related to specific resistance it acts on organisms having specific antigens only. The antigen upon detection triggers the production of the specific antibody against it.
Ex- When macrophages detect antigens they trigger the production of T-cells. There are hundred types of T-cell in blood but each one is specific only for a specific antigen. These T cells then give protiens that carries out the cytotoxic T-cell pathway against the specific pathogen.
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