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The Body’s Defenses Chapter 40 Objectives • Describe how skin & mucous membranes defend the body. • Compare the inflammatory response with the temperature response. • Identify proteins that kill or inhibit pathogens. • Analyze the roles of white blood cells in combating pathogens. Key Terms • Pathogen • Complement System • Mucous Membrane • Interferon • Inflammatory • Neutrophil Response • Macrophage • Histamine • Natural Killer Cell Pathogens • A pathogen is a disease causing agent. • Examples: – Harmful bacteria – Viruses – Fungi – Protists First Line of Defense Non - Specific First Line of Defense • Skin • Nearly impenetrable barrier • Reinforced w/ chemical weapons to inhibit pathogen growth – Oil – Sweat: contains an enzyme which digests bacterial cell walls First Line of Defense • Mucous Membranes are layers of tissue that produce a sticky, viscous fluid called mucous. • Examples: – Digestive System – Nasal Passages – Lungs – Respiratory Passages – Reproductive Tract What Happens if A Pathogen Gets Through the First Line? • Four things happen 1. Inflammatory Response 2. Temperature Response 3. Special Proteins that kill or inhibit pathogens 4. White Blood Cells, which attack & kill pathogens Second Line of Defense The Inflammatory Response • An inflammatory response is a series of events that suppress infection & speed recovery. • Injured cells release chemicals, including histamine – Causes local blood vessels to dilate, increasing blood flow. – Increase blood flow brings more white blood cells (WBCs) Inflammatory Response Second Line of Defense Temperature Response • Body temperature increases several degrees above the normal value. • Fever is helpful b/c many disease-causing bacteria do not grow well @ high temperatures. • Extremely high temperatures are dangerous b/c it can destroy important cellular proteins. Second Line of Defense Special Proteins • Complement System – consists of about 20 different proteins. – Proteins circulate in the blood & become active when they encounter certain pathogens. – Some proteins form a membrane attack complex (MAC), which punches a hole in the cell membrane, causing the cell to leak & die. Second Line of Defense Special Proteins • Interferon – a protein released by cells infected w/ viruses. – Causes nearby cells to produce an enzyme that prevents viruses from making proteins & RNA. Second Line of Defense White Blood Cells • Most important counterattacks in the second line of defense • 3 Types – Neutrophils – Macrophages – Natural Killers • Each kind uses a different mechanism to kill pathogens White Blood Cells Natural Killer Cell Macrophages White Blood Cells • Neutrophils – engulfs & destroys pathogens – Most abudent, kill the pathogen & themselves; can squeeze btwn cells in the walls of capillaries White Blood Cells • Macrophages – ingest & kill pathogens – Clear dead cells & other debris; concentrated in the spleen & lungs White Blood Cells • Natural Killer Cells – attacks cells infected w/ pathogens – Punctures the cell membrane causing water to rush in, in turn causing swelling. The cell will eventually burst. – Best defense against cancer Review • Often take the first stand during an infection. They attack any invaders in large numbers, and "eat" until they die. • Are slower to respond to invaders than the granulocytes, but they are larger, live longer, and have far greater capacities. Macrophages also play a key part in alerting the rest of the immune system of invaders. • Are "eater" cells and devour intruders, like the granulocytes and the macrophages. And like the macrophages, the dendritic cells help with the activation of the rest of the immune system. Immune Response Chapter 40 Section 2 Objectives • List four kinds of immune system cells, and describe their functions. • Describe how white blood cells recognize pathogens. • Identify the role of higher T cells in the immune response. • Compare the role of T cells with that of B cells in the immune response. Key Terms • Cytotoxic T cell • B cell • Helper T cell • Antigen • Plasma cell • Antibody What happens when pathogens occasionally overwhelm your body’s nonspecific defenses? Third Line of Defense Specific Third Line of Defense Immune Response • Not localized in the body • Not controlled by a single organ • More difficult to evade • Consists of individual cells that rush throughout the body to combat specific invading pathogens Cells Involved in the Immune Response • Four main types of White Blood Cells (WBCs) – Macrophages: consume any pathogen & infected cell – Cytotoxic T cells: attack & kill infected cells – B Cells: label invaders for later destruction by macrophages – Helper T cells: activate both cytotoxic T cells & B cells • B cells & T cells respond only to pathogens for which they have a genetically programmed match Antigens • An antigen is a substance that triggers an immune response. • Typically include proteins & other parts of viruses or pathogen cells. • Present on the surface of the infected body cell • WBCs are covered w/ receptor proteins that bind to specific antigens Antigens Killer T-Cells Memory Cells Disease Transmission & Prevention Chapter 40 Section 3 Objectives • List five ways diseases can be transmitted to humans. • Analyze how the body produces immunity to pathogens. • Describe how vaccines produce immunity to pathogens. Key Terms • Koch’s postulates • Immunity • Vaccination • Vaccine • Antigen shifting 5 Different Ways of Disease Transmission 1. Person-to-Person contact (communicable) 2. Air 3. Food 4. Water 5. Animal bites Long-Term Protection • The specific immune response is very powerful, & can be a long-lasting defense • B cells & T cells become memory cells that continue to patrol your body’s tissues. • If the pathogen ever appears again, memory cells activate antibody protection. • Second exposure to the same pathogen causes a sharp increase in antibody concentration. Resistance to Disease • Resistance to a particular disease is called immunity. • Vaccination is a medical procedure used to produce immunity. • A vaccine is a solution that contains a dead or weakened pathogen or genetic material from a pathogen. – Triggers an immune response against the pathogen w/o symptoms of infection Antigen Shifting • You can get the flu even if you have already been infected or vaccinated. • Influenza viruses constantly mutate over time • Viruses produce new antigens that you immune system does not recognize • W/ subsequent exposure to the virus, your body must make new antibodies Disorders of the Immune System Chapter 40 Section 4 Objectives • Describe several auto-immune diseases. • Summarize how HIV disables the immune system. • List five ways HIV is transmitted. • Identify causes of an allergic reaction. Key Terms • Autoimmune disease • AIDS • HIV • CD4 • Allergy Autoimmune Diseases • In an autoimmune disease, the body launches an immune response against its own cells, attacking body cells as if they were pathogens. Common Autoimmune Diseases AIDS • Before 1981 AIDS was unknown • Between 1981-2000, more than 448,000 Americans died of AIDS • Total number of people living w/ HIV in the US has increased to more than 850,000 • AIDS is a disease caused by HIV HIV • Many scientist think HIV evolved from a virus similar to one that infects nonhuman primates in Africa. • A mutation enables HIV to recognize a receptor protein called CD4 on some human cells. HIV • HIV enters WBCs by binding to CD4. • HIV usually invades helper T cells, which begin to produce HIV soon after infection. • When helper T cells die, the immune system gradually weakens & becomes overwhelmed by pathogens that it would normally detect & destroy. Testing for HIV • Antibodies for HIV can be detected in blood. • AIDS is diagnosed on several factors, including a helper T cell count less than 200 cells/mL of blood. Onset of AIDS AIDS • Time btwn HIV & AIDS can exceed 10 years • In the US, the number of deaths caused by AIDS: – 1996 – 38,000 – 1997 – 22,000 – 2000 – 15,000 • This is not due to a decrease in infections, rather more effective drug therapies, which postpone onset of the disease. Transmission of HIV • Contact with infected body fluids • Sexual contact • Sharing needles • Transfusions (many years ago) • Pregnant or nursing mothers to infants from blood & breast milk How HIV is NOT Transmitted • Through the air • Toilet seats • Kissing • Handshaking • Mosquitoes & ticks • HIV has been found in saliva, tears & urine however, they usually contain too few HIV particles to cause infection Allergic Reactions • An allergy is the body’s inappropriate response to a normally harmless antigen. • Include: – Pollen – Feces of dust mites – Fungal spores – Substances found in some foods & drugs
"The Body Defenses"