Immune System
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Immune System
Introduction
The human immune system is a complex system consisting of a network of numerous cells and cell types, tissues, and organs working together to defend the human body from foreign bodies such as invading microorganisms, infections, and tumors, while ignoring the normal working and healthy parts of the body.
Discussion
Working of the immune system
The immune system has different ways of identifying problems, communicating with other cells, and performing their activities. The immune system has the ability to distinguish healthy cells from unhealthy cells as it can recognize a number of different “danger” cues referred to as danger-associated molecular patterns (DAMPs). Infection is usually caused by infectious agents such as viruses and bacteria, which release another kind of signals referred to as pathogen-associated molecular patterns (PAMPs) to be identified by immune system (National Institute of Allergy and Infectious Diseases, 2013).
Researchers are of opinion that detailed understanding of the working of the immune system could help in fighting against a number of problems ranging from infections to cancer (National Institute of Allergy and Infectious Diseases, 2013).
Parts of the body having immune cells
Bone marrow is the part of the body from where immune cells are distributed to all other parts of the body. Immune cells can be found in the skin, bloodstream, lymphatic system, spleen, mucosal tissue, and other parts of the body (National Institute of Allergy and Infectious Diseases, 2013).
Figure 1: Presence of immune system in different parts of the body (Image credit: aids.gov)
Types of cells in the immune system
The bone marrow has common myeloid progenitor stem cells that can develop innate immune cells including eosinophils, neutrophils, mast cells, basophils, dendritic cells, and monocytes, and macrophages that are considered as first-line responders to different kinds of infection in the body (National Institute of Allergy and Infectious Diseases, 2013).
The bone marrow also possesses common lymphoid progenitor stem cells that can develop adaptive immune cells including B cells and T cells. These cells are helpful in fighting against certain microbes on the basis of their immunological memory, i.e. previous encounters with those microbes (National Institute of Allergy and Infectious Diseases, 2013). These cells are also involved in antibody-mediated immunity. In an antibody mediated immune response, macrophages interact with T helper cells and cause their activation. Those T helper cells stimulate a particular B cell that can help in making antibodies against the antigen that is causing the problem. The cell is stimulated, started dividing, and produces many exact copies (clones). Those clones start maturing and become Plasma cells that can produce lots of antibodies. The antibodies are proteins having specific shape to attach to antigens. Those antibodies are then secreted into the bloodstream, where they bind to a particular antigen and destroy the antigen. After controlling the infection, many of the cells are eliminated from the body. Whereas, some cells remain behind in the body as memory cells, so they would be able to work against the antigen in a faster manner in the future (The Pennsylvania State University, 2016).
Natural killer (NK) cells are also obtained from the common lymphoid progenitor. These cells possess the properties of both adaptive and innate immune cells as they not only provide immediate protection like innate cells but also possess some immunological memory like adaptive cells. Cells derived from common lymphoid progenitor stem cells are also referred to as lymphocytes (National Institute of Allergy and Infectious Diseases, 2013).
Types of immune defense. Surface coverage is the first line of defense in the body. Usually, skin and mucous membranes covers different parts of the body and protest it from pathogens (The University of Illinois, n.d.). On the basis of types of cells in the immune system, immune defense can be categorized into two types: Innate or nonspecific immune defense, which is also known as the second line of defense, and adaptive or specific immune defense, which is also known as the third line of defense. Complement proteins are plasma proteins in the body that are also involved in both nonspecific and specific defenses (The University of Illinois, n.d.).
Innate or nonspecific defense is present in the body at the time of birth and it works against various pathogens. This type of defense acts rapidly and includes chemical barriers, mechanical barriers, inflammation with the help of mast cells, and phagocytosis with the help of phagocytes. On the other hand, in adaptive or specific defense specialized lymphocytes works against specific pathogens, and this defense is more precise and target specific. Specific defense is third line of defense (Moini, 2015), as this defense starts working when first and second line of defense are not sufficient and infection becomes widespread in the body (The University of Illinois, n.d.).
Figure 2: Types of Immunity (defenses) (Image Credit: arcr.niaaa.nih.gov)
Problems arising as a result of disturbed immunity
Usually, infection occurs when the immune system is unable to be activated during the times of need. On the other hand, problem of allergic reactions and autoimmune disorders may occur, when the immune system starts working against the normal cells or does not stop after the danger passes (National Institute of Allergy and Infectious Diseases, 2013).
HIV infection/AIDS. One of the most serious problems arising as a result of disturbance in immunity is the infection caused by human immunodeficiency virus (HIV) that is also known as acquired immune deficiency syndrome (AIDS). HIV destroys the immunity by directly affecting the helper T cells in the body. Although the body tries to remove a number of HIV (viruses), but some of those viruses manages to live in the body and infect other T cells. After infection, those T cells start working for viruses and develop new viruses instead of removing them from the body. Moreover, many other normal T cells are destroyed in the process of making more HIV (viruses) (AIDS, 2011).
If the HIV infection is left untreated, it can destroy the immune system of the patient through a number of steps in HIV lifecycle. In the first stage of HIV lifecycle, i.e. acute HIV infection stage, the virus attacks and kills T-cells. Therefore, the T-cell count in the body decreases. During this stage, flu-like symptoms develop. After acute stage of HIV infection, clinical latency stage comes, when the virus is silent and there are no symptoms in the body. After clinical latency stage, AIDS comes; during which immune system is in its worse condition, T cell count in the body declines very much, and several other infections can develop (AIDS, 2011).
Conclusion
Immunity is one of the most important parts of our body. It is a blessing by nature that is protecting us from many diseases and infections. It can be said that our body is in a constant state of war against foreign invaders, and this war can only be fought with the help of immune system (Harun Yahya, 2011).
References
AIDS. (2011). How does your immune system work? Retrieved from https://www.aids.gov/hiv-aids-basics/just-diagnosed-with-hiv-aids/hiv-in-your-body/immune-system-101/index.html
Harun Yahya. (2011). The Miracle of the Immune System. https://www.youtube.com/watch?v=1w7Thma4Lqo: Harun Yahya.
Moini, J. (2015). Anatomy and Physiology for Health Professionals: Jones & Bartlett Learning.
National Institute of Allergy and Infectious Diseases. (2013). Overview of the Immune System. Retrieved from https://www.niaid.nih.gov/topics/immuneSystem/Pages/overview.aspx
The Pennsylvania State University. (2016). Steps in Antibody Mediated Immune Response. Retrieved from https://online.science.psu.edu/bisc004_activeup002/node/5372
The University of Illinois. (n.d.). The Immune System. Retrieved from http://bio100.class.uic.edu/lecturesf04am/lect23.htm
