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Transcript
Unit Two Immune System Pathogens Cause Disease • It is important to understand people become ill due to two main reasons: – Improper function of internal organs etc. – Infection caused by pathogen *** With proper preventative care, the incidence of infections caused by pathogens are minimal What are Pathogens • Pathogens are microorganisms that invade the human body (other species also). They cause damage to internal organ structure and the proper function of organs • There are three types of Pathogens: – Bacteria – Viruses – Prions Bacteria • • • • Prokaryotic DNA and Ribosomes only Cell Wall surrounds Plasma Membrane Obtain nutrients from a variety of sources including a “Host’s” cells • Shape is that of a Sphere, Rod, or Spiral • Most are harmless, and some are beneficial to digestion (think yogurt) Viruses • Smaller than Bacteria • Their structure consists of RNA/DNA surrounded by a Protein Coat protective layer • Are not considered living because they cannot replicate themselves without a “Host” • In order to replicate they must insert their genetic material (RNA/DNA) into the DNA of a Host’s cell….. This can spread to billions of the Host’s cells eventually causing death Prions • They are ill-formed brain cell proteins that infect and subsequently change the shape of other healthy brain cell proteins • Eventually the brain ceases to function due to all the ill-formed proteins • “Mad Cow Disease” is a Prion disease that first appeared in cows, then spread to the human population (mainly in Great Britain) • Not as common as viral and bacterial infections Pathogen Success • There are three factors that determine the evolutionary success of a pathogen: – Ease of Transmission – Mode of Transmission – Virulence Human Body’s Defense • The body’s immune system responds to pathogens/allergens with three levels of action: – Physical and Chemical Barriers • Skin, Hair, Mucus, Stomach Acid etc. – Innate /Nonspecific Response • Phagocyte action – Acquired/Specific Response • Lymphocyte action (B and T cells) Physical & Chemical Barriers • Skin – solid physical barrier that is acidic and constantly replaced • Tears – expels foreign contaminants • Earwax – prevents contaminants from gaining access to the ear canal • Mucus – similar function as that of tears and earwax • Vomiting – expels contents from stomach that may have pathogens • Urination/Defecation – expels waste material possibly contaminated with pathogens from body Innate/Nonspecific Response • If the pathogen is able to breach the external physical and chemical barriers now the body must actively seek out the intruder and destroy it • Also, after the pathogen is destroyed, the body must repair the damage done to it by the pathogen • Nonspecific Defense Mechanisms respond to all types of health challenges, including pathogen infections Innate/Nonspecific • Phagocytes – Neutrophils (1st responders) and Macrophages engulf and digest foreign cells; Eosinophils cluster around large parasites & excreting digestive enzymes to kill them • Natural Killer Cells – release chemicals that disintegrate cell membranes of tumor cells and virus-infected cells • Inflammatory Response – redness, warmth, swelling, and pain attract Phagocytes & promotes tissue healing • Interferons – stimulate the production of proteins that interfere with viral production • Fever – mid-grade fevers make environment less welcoming to pathogens Phagocytotic Process Acquired/Specific Response • Lymphatic System is responsible for three bodily functions: – defend the body against infection and injury – Maintain volume of blood in circulatory system – Transports fats and vitamins from digestive to circulatory system Lymphatic System Lymph Nodes • Lymph nodes are small organs in the Lymphatic System, • Located in the neck, armpit, and groin. • They remove microorganisms, cellular debris, and abnormal cells from the “Lymph” (milky fluid) before returning it to the Circulatory System (aka Cardiovascular System) • Recall Lymph comes from the portion of the blood plasma that diffuses out of the capillaries Spleen • One of the Spleen’s primary function’s is to fight infection • “Red Pulp” in the Spleen contains “Macrophages” that scavenge and destroy microorganisms, old/damaged red blood cells and platelets • The Spleen cleanses the blood (Red Pulp) and the Lymph Nodes cleanse the Lymph (Milky Fluid) Immune System and Antigens • An Antigen is a marker placed on a pathogen to identify it as a foreign invader; it causes an Immune Response • Lymphatic System responds by producing B and T cells • The B cells produce 5 types of Antibodies (GAME D) that sequester the Antigen marked Pathogen • The T cells then arrive to dispose of the Pathogen Lymphocytes • Lymphocytes play key role in the innate/specific defense mechanism • 2 types of Lymphocytes: – B lymphocytes • B cells mature in bone marrow • Responsible for antibody mediated immunity; focus on removing antigens from blood and lymph – T lymphocytes • T cells mature in thymus gland • Responsible for cell mediated immunity; focus on destroying infected cells B Cells • Responsible for antibody-mediated immunity • B cells produce antibodies – proteins that bind with and neutralize specific antigens • Often referred to as “Immunoglobulins” • B cells work best against viruses, bacteria, and foreign molecules that are soluble in blood and lymph • B cells mature in bone marrow, then travel via circulatory system to lymph nodes, spleen, and tonsils where they remain inactive until needed B Cells • When B cells become active, they reproduce additional cells to fight the antigen • Those new cells are called Clones/Plasma Cells • Some of the Clone Cells become Memory Cells – long lived cells that “remember” that initial antigen and can reactivate to attack it again if needed • Memory Cells store information about the pathogen, and as a result, the immune response is much quicker the second time infection occurs 5 Classes of Antibodies T Cells • Responsible for cell-mediated immunity • T Cells do not produce antibodies • Some T Cells directly attack foreign cells that carry antigens • Most T Cells release proteins that help coordinate the immune response: actions of T Cells, B Cells, and Macrophages • Cell mediated immunity protects the body against parasites, bacteria, viruses, fungi, cancer cells, and cells perceived as foreign (tissue rejection) T Cells • T Cells responsible for cell-mediated immunity develop from stem cells in bone marrow • T Cells mature in Thymus Gland • T Cells react to fragments of antigens, not the whole antigen T Cells • Types of T Cells include: – Helper T Cells: direct/enhance activities of many cell types in the Immune System – Cytotoxic T Cells: attack and destroy abnormal cells – Memory T Cells: reactivate upon later exposure to same antigen to form Helper and Cytotoxic T Cells – Suppressor T Cells: may suppress immune response after an antigen has been destroyed Immune System Facts • Immunity – body does not suffer the effects of the pathogen as a result of Memory Cells facilitating a Secondary Immune Response that is quick and decisive • Immunization – injection of monoclonal antibodies and antibiotics into the body to assist with the immune response • Vaccine – an “active immunization” which involves the injection of weakened antigens into the body with the intent of enabling the body to produce Memory Cells to fight the pathogen if it reenters the body in a healthy state (secondary immune response) Immune System Facts • Active Immunity develops after a primary immune response which is a response to exposure to a live pathogen and development of symptoms. The cells produce the antibodies themselves. (see vaccine) Passive Immunity is when a person's cells do not produce the antibodies, they receive them by an injection of antibodies or antitoxin. Immune System Facts • Monoclonal Antibodies – produced in a lab from cloned descendants of a single hybrid B Cell • Antibiotics – drugs that kill or inhibit growth of bacteria; when discovered were derived naturally, now are synthesized in a lab • Allergy – inappropriately strong response of the Immune System to an allergen • Allergen – any substance that causes an adverse bodily reaction HIV/AIDS • History – First documented in January of 1981 by the Center for Disease Control – Thought to have spread to the USA by a gay flight attendant who traveled abroad – Originally called the “Gay Cancer” and/or “Gay Plague” because the initial outbreak was mainly confined to homosexual males HIV/AIDS • History continued – Less than a year later the list of at risk individuals expanded to include intravenous drug users, recent Haitian immigrants, and Hemophiliacs regardless of sexual orientation – The virus that causes AIDS was first discovered by a French scientist in 1983 – Circa 1987, Rock Hudson announced he had AIDS and died shortly after HIV/AIDS • History continued – In the 1990’s heterosexual celebrities and professional athletes announced they too had acquired HIV: Magic Johnson and Arthur Ashe – The 1990’s saw large amounts of research dedicated to treatment drugs and finding a cure – Currently there are some very effective drugs to treat HIV and keep it from developing into AIDS – Majority of new cases are in Sub-Saharan Africa, and unfortunately those people lack the finances to pay for those drugs to treat HIV HIV/AIDS • Three phases of the disease – Acute Phase • Virus infects person (host) and replicates ferociously • Replication process causes death of lymphocytes in the person’s blood • Person may be asymptomatic for several weeks; if person does have symptoms they include fever, chills, aches, swollen lymph nodes, and an itchy rash • After many weeks the person’s body reacts to the foreign invader by producing numerous immune cells to fight the virus • HIV virus targets Helper T Cells by using that cell’s DNA to replicate its genetic information (RNA) to produce many more viruses HIV/AIDS – Chronic Phase • Several months to several years an untreated individual will most likely progress to this phase • The continued replication of viruses in the host T Cells leads to the body’s inability to fight off common infections because the Immune System is essentially destroyed • Number of HIV viruses increases causing reemergence of symptoms like fatigue, persistent fever, night sweats, persistent cough, and persistent diarrhea • These symptoms are a signal that full blown AIDS will develop soon HIV/AIDS – AIDS • Lymphocyte count has dropped drastically; viruses have taken over the blood • Person is extremely weak and thin due to persistent diarrhea and coughing • Person eventually dies due to the presence of another infection • People do not die from AIDS, but rather, Acquired Immune Deficiency Syndrome weakens their bodies ability to fight other common infections *** There is currently no cure for HIV/AIDS HIV/AIDS • In 2010, people can live for many years with HIV/AIDS due to the presence of drugs that keep the replication process to a minimum • If you are poor, and especially if you live in a less developed nation, you may not have access to these powerful drugs • AIDS is deadly; the best course of action is to not be exposed to the virus • It is worth noting, the method that is 100% effective at preventing exposure to AIDS and other STD’s is Abstinence • Update 7/8/2010: http://www.foxnews.com/story/0,2933,596242,00.html?te st=latestnews