LO1- Immune System

• Immune system is a defense mechanism that recognizes and responds rapidly to protect agains invasion from foreign agents and organisms like viruses, bacteria, toxins, and chemicals
• Two types of immunity are innate and adaptive, which works collectively against antigens to provide the body's first and second line of defense
• WBCs that are involved in the immunity are produced in the bone marrow
• B cells mature in the bone marrow
• T cells move from the bone marrow to the thymus to mature
• The spleen acts like a filter. The red pulp destroys the old and injured RBCs. White pulp has concentrations of lymphocytes
• The lymph nodes are distributed throughout the body and remove foreign material from lymph system before it reaches the blood stream
• Natural Immunity is present at birth and the first line of defense. It protects the host without memory. It acts to control and eliminate pathogens through the production of cytokines
• Cells that are involved in natural immunity are macrophages, dendritic cells, NK, basophils, eosinophils, and granulocytes
• Neutrophils are the first to arrive in inflammation
• Eosinophils and basophils increase in number during allergic reactions and stress responses
• Monocytes engulf, ingest, and destroy toxins
• The inflammatory response is the major function of the immune system that is elicited in response to injury
• Chemical mediators assist inflammatory response by minimizing blood loss, wall off invader, activate phagocytes, and promote scar tissue formation
• Physical barriers filter and clear skin, mucus membranes, cilia, cough, and sneeze
• Chemical barriers remove or destroy mucus, gastric acid, enzymes in tears/saliva, and sweat
• Immune regulation balances system to ensure response is strong enough to kill, but not destroy itself
• Acquired Immunity develops after birth. It is the 2nd line of defense. It makes "immune memory" from prior exposure
• Active adaptive immunity are defenses developed by the persons own body from previous infection or immunization lasting for years or life
• Passive adaptive immunity is a temporary transfer from a source outside the body that has developed immunity through previous disease or immunization
• Examples of passive immunity include transfer or antibodies from the mother to an infant, breastfeeding, or receiving injections
• Phagocytes ingest foreign particles and destroy invading agent. They also remove body's own dying or dead cells
• Aptosis is the body's way of destroying worn out cells like blood or skin cells that needs to be renewed
• Humoral response is also known as the antibody response. It begins with B cells recognize and respond to invaders -> antibody production is triggered -> B cell proliferation and development of memory cells
• Cellular response involves T cells which turns to cytotoxic cells taht can attack pathogens
• In the recognition stage, antigens are recognized by circulating lymphocytes and macrophages.
• In the proliferation stage, the dormant lymphocytes proliferate and differentiate into cytotoxic (killer) T cells or B cells responsible for formation and release of antibodies. 
• In the response stage, the cytotoxic T cells and theB cells perform cellular and humoral functions, respectively.
• In the effector stage, antigens are destroyed or neutralized through the action of antibodies, complement, macrophages, and cytotoxic T cells.
• An antigen is a substance that the body recognizes as foreign, triggering an immune response.  When antigens are introduced into the body, proteins called antibodies are produced in response.
• HIV is a virus that targets and damages the body's immune system which leads to an inability of the body to fight infection and disease
• HIV causes acquired immunodeficiency syndrome or AIDS