The Immune System Bryce Tappan

Function of the Immune System The purpose of the immune system is to protect an organism from external dangers such as microbes and chemicals.

Immunity: Major Organs and Body Parts Important components of the immune system include: lymphoid organs, adenoids, tonsils, thymus, spleen, lymph nodes, bone marrow eases/immunesystem/pages/index.aspx

How the Immune System Works The immune system detects pathogens by determining which cells are “self” cells and which are “foreign” cells. When a pathogen triggers an immune system response, it is known as an antigen. Antibodies combat antigens. -8&q=antigen+definition

Antibodies There are different types of pathogens- extracellular and intracellular. Generally, antibodies defend against extracellular pathogens. Antibodies can block pathogens from attaching to host cells by binding to them, therefore protecting the host cell. This is called neutralization.

Antibodies & Antigens When antibodies bind to antigens, the group becomes recognized by other cells as foreign. Phagocytes can then take action to destroy the antigen. The recognition and destruction of the antigen is called opsonization.

Intracellular Pathogens Because antibodies do not fight pathogens within cells, another method must be used to kill the pathogen. Infected cells release an antigen that is recognized by lymph cells. The lymph cells then induce the cell to destroy itself, which stops the spread of infection.

Innate Immunity First line of defense, protects against infections Immunity is in place before the antigen is present Does not discriminate between antigens Innate immunity can be improved after exposure to an antigen by cytokines

Acquired Immunity Triggered by presence of antigens that escape the innate immune system Shows extreme specificity towards antigens Becomes more effective the next time an antigen is present, “biological memory”

Active Immunity Active immunity is naturally acquired, and is created when an organism is infected by a pathogen and becomes immune to that pathogen thereafter. Vaccines are a way to artificially stimulate active immunity by exposing a weak strain of a pathogen so the body can build resistance.

Passive Immunity Passive immunity occurs when antibodies from one organism are passed to another to help fight against infection. The transfer of antibodies from a pregnant woman to the baby is an example of passive immunity.

Humoral Immunity Humoral immunity is facilitated by the use of antibodies that originate in B lymphocyte cells. The antibodies released from the B cells bind to antigens. This bond serves as an indication of what cells need to be destroyed; it’s a way of differentiating “self cells” from “foreign cells.” Humoral immunity takes place in the body fluids of an organism.

Cell-mediated Immunity Cell-mediated immunity deals with macrophages, natural killer cells, T-lymphocyte cells, and cytokines that respond to antigens. The T cells have the ability to cause invading cells or viruses to undergo apoptosis. Macrophages and natural killer cells destroy invasive cells as well. Cytokines can induce other cells of the immune system to respond to threats within the body. Cell-mediated immunity generally attacks microbes, cells infected by viruses, fungi, protozoans and even cancer.

B Lymphocytes B lymphocytes, a type of white blood cell, produce antibodies and are the main component of the humoral immune system, as well as playing a role in the adaptive immune system. B cells don’t make any antibodies until they are activated. B cells have specific membrane bound proteins called cell receptors that recognize particular antigens and bind to them, which makes them activated.

T Lymphocytes T cells are white blood cells involved in cell-mediated immunity. They differ from B cells in that they have a unique t-cell receptor on the surface of the cell. There are different types of t cells that perform different functions. Helper cells- These cells help other white blood cells perform immunologic tasks Cytotoxic cells combat viral infections and cancerous cells Memory T-cells are antigen specific, meaning that the next time the body is exposed to that specific antigen, the response will be quick and effective. Regulatory T-cells shut down the processes the body uses to fight an infection after the infection has been dealt with. Natural Killer T-cells also help fight viral infections and tumours

Antibiotics & Bacteria Antibiotics are a sort of “selective poison;” it singles out certain bacteria to kill but generally not somatic cells. Antibiotics work by inhibiting some of the different functions of single celled organisms use to survive. For example, some antibiotics can damage the bacteria cell walls, others attack the metabolism of bacteria. This speeds up the process of killing the bacteria. n/question88.htm

Immune System Disorder: Addison’s Disease 1)Addison’s disease is a serious endocrine disorder that causes the adrenal glands to produce insufficient steroids hormones. 2)Abdominal pains, fatigue, low blood pressure and even comas may occur. 3)Addison’s disease is extraordinarily rare. 4) Supplements, such as hydrocortisone tablets, may be used to provide the missing steroids and can alleviate the effects of Addison’s Disease.

HIV/AIDS 1)Acquired Immune Deficiency Syndrome is a disease caused by the Human Immunodeficiency Virus, which is often transmitted sexually 2)Once HIV has developed into AIDS, it hampers the immune system’s ability to defend against pathogens and diseases. 3)HIV/AIDS is considered a pandemic, and it has become more widespread in the last 20 years. An estimated 60 million people have been infected with AIDS since the 1980s. 4)Antiviral therapy- Medicines have been developed that inhibit the enzyme reverse transcriptase- the enzyme that allows the HIV virus to make copies of its genetic material and spread. Prevention is simply the most common way to fight against AIDS, which includes abstinence.