The Immune System

13.1 Infectious Diseases Main Idea: Pathogens are dispersed by people, other animals, and objects

Pathogens cause infectious disease Pathogen – agents that are the cause of infectious diseases Bacteria, viruses, protozoans, fungi, parasites Infectious disease – disease that is cause when a pathogen is passed from one organism to another, disrupting homeostasis in the organism’s body

Spread of Disease Pathogen must have both a reservoir and a way to spread Reservoir – source of the pathogen in the environment Animals, people, objects

Human reservoirs Main reservoir for pathogens that affect humans Can be symptom free and pass pathogen (carrier) Colds, flu, STDs Animal reservoirs Flu, rabies Other reservoirs Soil, water, food

Transmission of pathogens Direct contact Indirect contact Through the air Objects handled by humans Vectors Do not cause disease themselves but transmit pathogens from one host to another Mosquitos, flies, rats, ticks

Symptoms of Disease Virus - Pathogen invades cells and damages or kills them Bacteria – produce harmful chemicals or toxins that damage various parts of the body Some symptoms (coughing, sneezing) triggered by the immune system

Disease Patterns Endemic disease – continually found in small amounts within the population Examples: Epidemic – large outbreak of a disease in a particular area Examples: Pandemic – epidemic that is widespread throught a large region Examples:

Treating and fighting disease Antibiotic – substance that can kill or inhibit the growth of other microorganisms Penicillin – 1 st antibiotic discovered in 1940s Antibiotic resistance (natural selection)

13.2 The Immune System Main Ideas: White blood cells fight infection The immune system has two main components: nonspecific immunity and specific immunity

White blood cells NameFunction BasophilMakes chemicals that cause inflammation in the bloodstream Mast cellMakes chemicals that cause inflammation in other body tissues NeutrophilEngulfs pathogens and foreign invaders (phagocyte) MacrophageEngulfs dead or damaged body cells and some bacteria (phagocyte) LymphocyteDestroys infected body cells or produces proteins that inactivate pathogens EosinophilInjects poison into parasites

Nonspecific immunity Not aimed at a specific pathogen Protect the body from any pathogen the body encounters 1 st line of defense

Nonspecific immunity Barriers Skin Chemical barriers saliva, tears, nasal secretions contain lysozyme which kills pathogens Stomach acid – kills microorganisms in food Mucus secreted inside body Airway becomes infected  secretes extra mucus  coughing & sneezing to get infected mucus out

Nonspecific immunity Nonspecific response to invasion Cellular defense White blood cells (phagocytosis) Neutrophils & Macrophages Interferon Produced when virus enters body Antiviral protein secreted by virus infected cells Can prevent viral replication in cells

Nonspecific immunity Inflammatory response Increased blood flow to infected area helps white blood cells accumulate Basophils & mast cells

Nonspecific immunity Fever Mast cells or macrophages release chemicals that cause the hypothalamus to increase the body’s temperature Low fevers stimulate the production of interferons and increase activity of white blood cells High fevers are dangerous

Specific Immunity B Cell Response White blood cell (lymphocyte) Produce proteins (antibodies) that inactivate pathogens that have not yet infected a body cell Antibodies – proteins that specifically react with a foreign antigen Can cause pathogens to clump, making them easier for phagocytes to destroy Can also initiate inflammatory response

Specific Immunity T Cell response Helper T cell – lymphocyte, activates antibody secretion Cytotoxic T cell – bind to pathogen, destroy pathogens and release cytokines Cytokines – stimulate cells of immune system to divide and recruit immune cells to an area of infection

Passive Immunity Occurs without the body undergoing an immune response Genetic immunity – pathogen not specialized to harming that species Inherited immunity – pathogen fighting antibodies in mother’s immune system passed to child

Active Immunity Immunity that your body produces in response to a specific pathogen that has infected or is infecting your body Keeps you from becoming sick by a particular pathogen more than once

Active Immunity Memory cells – specialized B and T cells that provide acquired immunity because the “remember” an antigen that has previously invaded Comes across antigen and destroys it before the body has a chance to get sick

Active Immunity Immunization (vaccination) – deliberate exposer of the body to an antigen so that memory cells will develop Contain weakened or killed pathogens that are incapable of causing the disease Most require “booster shot” to increase immune response and provide further protection

13.3 Overreaction of the Immune System Allergies occur when the immune system responds to harmless antigens. Allergens – antigens that cause an allergic reaction

Allergies Allergen enters the body  mast cells or basophils release histamine and cause inflammation response Cause is unknown Genetics? Exposure to allergen too early in life?

Allergies Anaphylaxis- immune system releases large amount of histamine causing airways to tighten and blood vessels to become porous Can result in death

Allergies Food allergens 1-2% of adults & 5-8% of children Most common: milk, eggs, peanuts and tree nuts, soy, wheat, fish, shellfish

Allergies Airborne allergens Cause allergic response when breathed in Allergy season – plants and molds reproduce and release spores into the air Pet dander Can cause asthma

Allergies Chemical allergens Metals – 10% of population Venom from bee stings Penicillin

Autoimmune disease White blood cells attack the body’s healthy cells Immune system cannot tell difference between healthy & unhealthy cells Body treats its own cells as though they are foreign invaders Possibly genetic component Triggered by virus, drug, or environmental toxin

Autoimmune Disease Body System Affected The immune system… How many affected Rheumatoid arthritis IntegumentaryBreaks down tissues that line joints, making movement difficult 70 in 10,000 Type 1 diabetesEndocrine, digestive Attacks pancrease, stopping the digestion of sugars 60 in 10,000 Hashimotos thyroiditis EndocirenAttackes the thyroid gland causing it to make fewer hormones 15 in 10,000 Multiple sclerosis (MS) NervousBreaks down myelin sheaths, disrupting nerve communication 10 in 10,000 Graves’ diseaseEndocrineStimulates thyroid gland causing it to make more hormones 5 in 10,000