THE IMMUNE SYSTEM NONSPECIFIC IMMUNITY NonSpecific Defenses not

THE IMMUNE SYSTEM

NON-SPECIFIC IMMUNITY Non-Specific Defenses: not aimed at a specific pathogen, protects the body from any pathogen that the body encounters I. Barriers Skin Barrier: prevents foreign organisms from entering the body � Consists of unbroken skin and secretions � Dead skin cells help protect against invasion � bacteria on skin’s surface protect it from attack

CHEMICAL BARRIERS 1. Common examples include saliva, tears, and nasal secretions � All contain lysozyme, an enzyme that breaks down bacterial cells 2. Hydrochloric Acid: secreted in stomach; kills microorganisms found in food

3. Mucus: secreted by many inner surfaces of the body � protective barrier that prevents bacteria from sticking to inner epithelial cells � when sick, extra mucus is secreted which causes coughing/sneezing to remove infected mucus � Cilia: hair-like projections that line the airway � Sweeps away trapped bacteria

NON-SPECIFIC RESPONSES TO INVASION If a pathogen gets past the barriers, the body continues to defend itself Cellular Defense: 1. Phagocytosis: phagocytic cells surround and internalize (consume) foreign organisms, then destroy them using digestive enzymes/lysosomes � White blood cells (neutrophils and macrophages) � Complement Proteins: enhance phagocytosis by

2. Interferon: a protein secreted by virusinfected cells � Binds to nearby cells and makes them produce antiviral proteins which can prevent viral replication

3. Inflammatory Response: involves many chemicals and immune cells that enhance immune response � Pathogens damage tissue, releasing chemicals by both the invader and the body cells � Chemicals attract phagocytes to area, increase blood flow to infected area, and make blood vessels more permeable (allow white blood cells to enter infected area) � Sometimes accompanied by pain, heat, and redness

SPECIFIC IMMUNITY Specific Immunity: more effective, but takes time to develop; involves tissues and organs found in the lymphatic system Lymphatic system: organs and cells that filter lymph and blood and destroy foreign microorganisms Lymphatic organs: made up of lymphatic tissue, lymphocytes, and connective tissue Lymphocytes: type of white blood cell that is produced in red bone marrow

B CELL RESPONSE Antibodies: proteins produced by B lymphocytes that specifically react with foreign antigens Antigen: a substance foreign to the body that cause an immune response � Binds to an antibody or T cell

B lymphocytes (or B cells): found in all lymphatic tissues, like antibody factories � When portion of pathogen is presented by a macrophage, B cells produce antibodies

� When a macrophage surrounds and consumes a pathogen, it absorbs a piece of it and displays it on its membrane. The macrophage with the processed antigen then binds to a helper T cell (a type of lymphocyte). The helper T cells then become active. � Activated helped T cell reproduces, binds processed antigens, and attaches to B cell

�B cell begins to produce antibodies that specifically bind to antigen � Antibodies enhance immune response by binding to microorganisms, increasing rate of phagocytosis

T CELL RESPONSE � Activated helper T cells activate a group of lymphocytes called cytotoxic T cells Cytotoxic T Cells: destroy pathogens and release chemicals called cytokines � Stimulate immune system cells to recruit more cells � Bind to pathogens, release a chemical attack, and destroy the pathogens

PASSIVE AND ACTIVE IMMUNITY Primary Response: the body’s first response to an invasion by a pathogen � Produces memory T and B cells – remember pathogen and respond if the body encounters it again Passive Immunity: temporary protection against an infectious disease � antibodies made by others are transferred or injected into body � Ex. Mother and child – mother’s antibodies are passed to the child through breast milk

Active Immunity: occurs after immune system is exposed to disease antigens and memory cells are produces � Can result from having an infectious disease or vaccination

Vaccination (or Immunization): deliberate exposure of the body to an antigen so that primary response/memory cells develop � Contain killed or weakened pathogens, which are incapable of causing the disease � Include initial exposure, then one stimulus later (a booster shot)