Immune Responses to Microorganisms

Innate immunity is also referred to as non-specific defence mechanisms, and it reacts to antigens when they arrive in the body. The innate immunity system is referred to as non-specific due to its reaction to a wide variety of antigens with a repeated general response. The non-specific defence mechanism reacts within minutes after an antigen or foreign agent attacks the body. The innate immune system has several other names that include natural, antigen-specific, and emergency response system.

The other defense system in the body is the adaptive system, also referred to as the acquired immune system. The adaptive system is activated after the innate system is fully activated. Unlike the innate immunity, adaptive system is specific in nature as it reacts a particular way to particular antigens as opposed to providing a general response to the various antigens. The adaptive system is slower in terms of reaction time after invasion by a foreign agent thus its complex system. The complex system starts first by recognizing the antigen that has invaded the body before creating an immune cells army that will retaliate against the antigen.

The two immune systems have varying components that constitute the whole system. The innate immunity comprises of the physical barriers such as the skin, chemical barriers, phagocytic cells, natural killer cells and complementary proteins. The skin and the mucous membrane are the outermost defense system in the innate system. This mechanical barrier is critical in preventing the pathogens from entering the body. The mucous membrane contains various substances such as mucus, enzymes and acids that act as the chemical barrier for viruses and bacteria. Other forms of outside protection include sweat, movement by bowel muscles, and urine rinsing.

The other form of protection by the innate immune system is from inside. It is possible for the antigens to pass through the first line of defense, thus activating the second line of defense. The second line of defense comprises of inflammatory cells or defense cells. The area of infection is also defended by activation of soluble proteins. Phagocytes or scavenger cells are responsible for eliminating the pathogens on the spot (Cooper & Koprowski, 2013). The most effective defense cells are found in the tissues – macrophages, and the blood – neutrophil granulocytes. These defense cells work by enclosing and digesting the pathogens in their interior. An enzyme chain reaction is essential in improving the innate immunity system. The third line of defense is the natural killer cells that look for cells with changed surfaces or infected with viruses. They produce cytotoxins – cell poisons, which dissolve the affected cells.

The adaptive system come in when the innate immune system has failed to defend the body from antigens. It takes longer than the innate system to respond as it can respond even after seven days. The adaptive immune system is more accurate than its counterpart as it targets a pathogen. Furthermore, the system remembers the antigen, as it produces memory cells, and if there is new contact in the future with the same foreign body, it can remember and act quicker. In general, the adaptive system is more fast and efficient than the non-specific immune system.

The adaptive immunity comprises of humoral immunity and cell-mediated immunity. The humoral immunity comprises of the B cells (lymphocytes) and plasma cells, while the cell-mediated immunity comprises of the T cells (lymphocytes). The B lymphocytes are responsible for the production of antibodies and they are specialized for a particular antigen. The act by binding to the surface of the defense cells. The T lymphocytes are produced in the bone marrow and mature in the thymus gland. They recognize the infected cells and eliminate them as the pathogens can bind on their surface and creating other T cells. In the defense reaction, the T cells produces other cells that include T helper cells, T killer cells, memory T cells and regulatory T cells.
The other differences between the two immune systems are that innate immunity can be inherited from the parents, but adaptive immunity cannot. The diversity of response in the innate immunity is low, but the one for adaptive immune system is high. Once the innate immunity is activated against a specific pathogen, the immunity remains throughout life, but the immunity can stay for life or be short for the adaptive immunity.








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