The+Immune+System

[Chi]

What is a pathogen? -A **pathogen** or **infectious agent** — colloquially, a **germ** — is a [|microbe] or [|microorganism] such as a [|virus], [|bacterium] , [|prion] , or [|fungus] that causes [|disease] in its [|animal] or [|plant] [|host].

How are pathogens related to homeostasis? -Homeostasis is the property of a system, either [|open] or [|closed], that regulates its internal environment and tends to maintain a stable, constant condition, typically used to refer to a living [|organism]. It takes every part of the system to work, together, properly to maintain homeostasis. Specific types of pathogens typically attack one specific part, leading to difficulties caused for the entire system, making it hard to maintain homeostasis.

What is the role of the skin (integumentary system) in defending against pathogens? - -Beneficial bacteria that live on the skin provides protection by releasing acids and wastes to kill off unwanted microorganisms.  The layer of overlapping dead cells on the surface of the skin prevents pathogens from entering the body. A break in the skin gives pathogens access to body tissues. If this happens blood clots then form a temporary barrier until new skin seals the wound.

How do inflammation and fever help the immune system? -Fever can support the immune system's attempt to gain advantage over infectious agents, such as viruses and bacteria, and it makes the body less favorable as a host for replicating viruses and bacteria, which are temperature sensitive.

How do B cells function? **-B cells ** differentiate into **plasma cells** that secrete **antibodies**. Antibodies are proteins that bind to specific antigens and mark them for destruction by, for example, marking them more recognizable to phagocytic cells. In this way, B cells "flag" cells for destruction by macrophages. B lymphocytes and antibodies respond primarily to bacteria and bacteria toxins in our body fluids.

How do T cells function? -T cells (also called T lymphocytes) are white blood cells that defend the body from infectious disease, cancer, and foreign substances. T cells also release chemicals (interleukins) that control the entire immune response, that is, how the body recognizes and defends against disease and infection.

 Helper and Killer T Cells
Helper T cells circulate in the body hunting for diseased or infected cells. When the helper T cells find these unwanted cells, the helpers send a signal to the killer (cytotoxic) T cells to come and kill the diseased or infected cells. The helper T cells also tell the B cells (another type of white blood cell, also called a plasma cell) to produce antibodies needed to fight off infection. <span style="font-family: 'Georgia','serif'; font-size: 10pt;">Killer T cells are important because they are the only T cells that can directly attack and kill other cells. Activated (or "turned on") cytotoxic T cells kill cells that contain foreign particles (antigens) by attaching to them and injecting a toxic chemical.

<span style="font-family: Georgia,serif; font-size: 10pt; margin-bottom: auto; margin-left: 0in; margin-right: 0in; margin-top: auto;">Suppressor and Memory T cells
<span style="font-family: 'Georgia','serif'; font-size: 10pt;">Suppressor T cells (also called regulatory T cells) tell the immune system when the fight with the diseased or infected cells is over, and the killer T cells are no longer needed. Regulatory T cells are important in preventing an overactive immune system. Problems with the regulatory T cells can lead to autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis, and lupus. <span style="font-family: 'Georgia','serif'; font-size: 10pt;">Another problem that can occur is an inappropriate immune response when the body encounters a harmless substance, such as pollen. The result is allergies. Allergies are basically a wrong response from the immune system. <span style="font-family: 'Georgia','serif'; font-size: 10pt;">After the body fights off the threat of disease or infection, some T cells remain in circulation as memory T cells. Memory T cells retain information about the pathogen they encountered, so if it shows up again, the body recognizes it and quickly begins to respond.

[Maria] When an antigen enters the body, symptoms of disease may appear while the immune system is making antibodies to fight it. In immune system, there are **antibodies**, which are created by B cells. It can prevent and destroy the pathogens by binding the pathogen’s membrane proteins (Nowicki) [Maria]. Antibodies are proteins that help body to fight against antigen. Antigens can be bacterias, viruses or fungi that can cause diseases for our body. Antibodies attach themselves to the fitted antigens and then inactivate it. Antibodies are known as Y-shaped. ("Antibody and antigen")

(antibody)

**Bacteria** and **viruses** have some differences, and also similarities. The differences between bacteria and viruses are: <span style="font-family: Georgia; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;">Bacteria are single-celled organism (prokaryote), which is alive and can release chemicals (toxics) to destroy the host cells, which leads to illness (Nowicki 942) [Maria]. <span style="font-family: Georgia; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;">Viruses are diseases causing strands of DNA or RNA surrounded by protein coats. It can take over one healthy cell and make it stop function properly, and then produce more viruses (Nowicki 942) [Maria]. <span style="font-family: Georgia; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;">And the similarity which bacteria and viruses share is that they both can cause serious illness to one body (Nowicki 942) [Maria]. (bacteria)

(“Cellular Laboratory”)

To prevent the bacteria, the immune system uses the white blood cells (eosinophil), antibodies and complement proteins (Nowicki 946) [Maria]. <span style="font-family: Georgia; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;">To prevent the viruses, the immune system uses phagocytes, interferons, which are designed to fight and protect the body (Nowicki 946) [Maria].

<span style="font-family: Georgia; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px;">The **vaccines** role in immune system is that it contains the antigen of a pathogen. And from that can help it creates memory B cell. Also they can produce/make antibodies faster, prepare when the pathogens come (Nowicki 956) [Maria]. (vaccine)

**HIV-** This virus lives in and kills helper T-cells. With fewer helper T-cells, the person’s immune system can’t form any new antibodies against any new invade ("Immune System"), because T cells give signals for B cells to make antibodies to prevent pathogens, making the body gets vulnerable and easily to get diseases. Also, the HIV can control the immune response system. The T cells can’t be reproduced fast. So once it’s destroyed by HIV, leaving the body can’t defend it itself from the diseases (Nowicki 961) [Maria]. (hivvirus)

For more basic information: -[] (Know about lymphocites, which are a type of white blood cells that fight against infection) -[] (Useful website with information about AIDS, interferon, and mostly vaccine)


 * Works Cited **

<span style="font-family: Georgia; margin: 0px 0px 0px 0.5in; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px; text-indent: -27pt;">Nowicki, Stphen. "Immune System and Disease." //Biology//. Canada: McDougal Littel, 2008. 938-54. 2-03240. //McDougal Littel Biology//. McDougal Littel. Web. 14 May 2011.