Immune+System

//__**The immune system:**__//

The immune system is the body's defense against infectious and diseases. By using the stages of the immune response, the immune system attacks any causes of disease or infection throughout the the body. The immune system is made up of many cells, tissues, and organs that together help to protect and free the body from harm. The first link in the chain of infection is the pathogen. A pathogen is anything that causes disease.The inner body needs to maintain homeostasis but pathogens mess with homeostasis.

Cell types: B cells produce antibodies. Antibodies are a type of protein which fights off invading pathogens, they make pathogens ineffective. T cells are cells which destroy infected cells. SOmetimes white blood cells cause tissue rejection after an organ or tissue transplant because they move toward the infection and damaged tissues. White blood cells can recognize any particle or cell that is different from other cells in the body. Cellular immunity: Mainly T cells. Become activated and divide when they come across specific antigens. Humoral immunity: Mainly B cells. T cells activate the b cells, which divide and mature.

Vaccines: A vaccine contains a killed, destroyed or weakened part of a germ, that causes infection. Because the germ has been killed or weakened before, they use it to create the vaccine, this cannot harm or make the person sick.

HIV: The action of the human immunodeficiency virus (HIV) in the human body is a retrovirus which attacks and weakens the immune system, as well as being transmitted by mixing infected blood with a bodily fluid. The body has difficulty defending against bacteria, viruses and even HIV. It is mainly difficult defending against HIV because HIV reproduces in and destroys T cells, which then cannot be replaced fast enough, the T cells can't help in the immune responses

Inflammation and Fever: Inflammation and fever are called nonspecific immune responses becasue their responses occur the same way for every pathogen. Innflammation occurs when white blood cells release the chemicals which cause blood vessels to become leaky, this allows phagocytes to come out of the circulatory system and head towards an infection site. Fever is the increased body temperature, and the maturation of white blood cells which help to fight off infection.



__//**Vocabulary**//__
 * **Pathogen:** Anything that causes disease
 * **Immune system:** The body system that fights off infection and pathogens.
 * **Phagocytes:**
 * **B cells:** Produces antibodies
 * **T cells:** Destroys infected cells
 * **Antibodies:** Make pathogens ineffective
 * **Interferons:** Prevent viruses from infecting healthy cells.
 * **Passive immunity:** Occurs without an immune response, - Mothers milk - Genetics
 * **Active immunity:** Occurs after a specific immune response.


 * **Inflammation:** When blood vessels become leaky
 * **Antigens:** Surface proteins on pathogens
 * **Memory cells:**
 * **Cellular immunity:** Uses T cells to destroy infected body cells.
 * **Humoral immunity:** Uses B cells to produce antibodies.