Adaptive Immunity

Fourth Line of Defense Adaptive Immunity: specific immune system that is made up of specialized cells that eliminate pathogens or prevent their growth after exposure Specific lymphocytes remember the pathogens you have been exposed to and know to respond to them

Antigens Cell -surface protein that tells the body what type of cell it is Two Types: Foreign Antigens: antigens introduced from outside the body Ex: Antigens from bacteria, viruses, etc. Self-Antigens: antigens produced by the body Ex: Antigens from tumors signaling their destruction

Antibodies Proteins that bind to bad antigens and lead to their destruction

Cells Involved in Adaptive Immunity

Lymphocytes Are responsible for adaptive immunity in your body Two Types: T Cells: attack infected cells B Cells: attack pathogens outside cells

T Cells Produced in red bone marrow, but mature in the thymus Responsible for Cell-Mediated Immunity Cytotoxic T Cells: Kill infected cells by releasing chemicals Helper T Cells: Activate B cells and Cytotoxic T cells Memory T Cells: Remember pathogens after exposure

B Cells Originate and mature in red bone marrow; differentiate to fight infection Plasma Cells: Produce antibodies to attack infection Memory B Cells: Remember pathogens after exposure

Lymphocyte Activation After Memory B and T cells have been exposed to a pathogen they remain in the lymph nodes until they are exposed to the pathogen again Then they will activate and start to reproduce Ex: Strep Throat

Lymphocyte Proliferation Normally the body only has a few lymphocytes that recognize each pathogen, so before they can fight the infection they must reproduce Two Types: Proliferation of Helper T Cells: Bind to dendritic cells and reproduce rapidly Proliferation of Other T Cells and B Cells: Helper T Cells Bind to the lymphocytes that recognized the pathogen and aid in their reproduction and differentiation

Antibody-Mediated Immunity B cells fight pathogens by making and releasing antibodies to attack a specific pathogen Plasma cells make the antibodies and release them into the bloodstream Antibodies bind to the antigens of infected cells or free floating pathogens and destroy them Methods of Destruction: Antigen Inactivation Causing antigens to clump together Activating the complement cascade Causing the release of chemicals from the immune system Enhancing phagocytosis Continues until told to stop by the brain Memory B cells are stored in the lymph nodes for future use

Cell-Mediated Immunity Caused by Cytotoxic T cells that directly attack pathogens or pathogen infected cells Release a chemical called perforin which causes infected cells to develop holes in their cell membrane and die

How the Immune Response is Stopped Regulatory T cells signal the immune response to stop