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Chapter 21: The Basics of the Immune System and the Innate Immune System
Terms in this set (47)
What is the function of the immune system?
-Functional system rather than an organ system
-Innate and adaptive defenses intertwined
-Release and recognize many of the same defensive molecules
What does the body defend against?
-Cell debris (Fragments of dead cells)
What is a pathogen?
-A microorganism that has the potential to cause a disease (bacteria, virus, fungus, parasite)
-An infection is the invasion and multiplication of pathogenic microbes in an individual or population
-Disease is when an infection causes damage to the individual vital functions of systems
-An infection does not always result in disease
What are cancer cells?
-Normal cells that have acquired mutations resulting in abnormal cell growth
-Many neoplastic cells are removed from the body during our lifetime
What is immunity?
-Resistance to disease
What are the two divisions of the immune system?
What is the innate immune system?
-Has the first two lines of defense
-First line: external body membranes (skin and mucosa)
-Second line: antimicrobial proteins, phagocytes, and other cells (Inhibits spread of invaders, inflammation is the most important mechanism)
What is the adaptive immune system?
-Third line of defensive attacks particular foreign substance (takes longer than the innate system)
What is the function of the innate surface defenses?
-Skin, mucous membranes, and their secretions
-Physical barrier to most microorganisms
-Keratin in skin resistant to weak acids and bases, bacterial enzymes, and toxins
-Mucosae provides similar mechanical barriers
What are the modifications in the respiratory system in the innate surface defenses?
-Mucus-coated hairs in the nose
-Cilia of the upper respiratory tract sweep dust- and-bacteria-laden mucus
What are the chemical barriers in the innate surface defenses?
-Protective chemicals inhibit or destroy microorganism
-Acidity of skin and secretions: acid mantle inhibits growth
-Enzymes: lysosomes of saliva, respiratory mucus, and lacrimal fluid (kills many microorganisms)
-Defensins: antimicrobial peptides- inhibits growth
-Other chemicals: lipids in sebum, dermcidin in sweat (toxic)
What happens when the surface barriers break?
-Once surface barriers breaks by a nicks or cuts, the second line of defense must protect the deeper tissues
What is the function of the innate internal defenses?
-Necessary if microorganisms invade deeper tissues
What are the internal defenses?
-Natural Killers (NK) cells
-Antimicrobial proteins (interferons and complimentary proteins)
-Inflammatory response (macrophages, mast cells, WBCs, and inflammatory chemicals)
What are the most abundant types of phagocytes?
-Neutrophils, they die fighting off infections (become phagocytic on exposure to infectious materials)
What are the cell stages that macrophages develop from?
-Robust cells, chief phagocytic cells, monocytes, macrophages
What is the function of helper T cells?
-T cells cause the release of enzymes of respiratory burst, which kills pathogens resistant to lysosomal enzymes by; releasing cell-killing free radicals, producing oxidizing chemicals, increasing pH and osmolarity of phagolysosomes
What is the purpose of defensins in neutrophils?
What is the first step in phagocytosis?
-Phagocytes adheres to pathogens or other debris
What is the second step in phagocytosis?
-Phagocytes forms pseudopods that eventually engulf the particles, forming a phagosome
What is the third step in phagocytosis?
-Lysosomes fuses with the phagocytic vesicles, forming a phagolysosome
What is the fourth step in phagocytosis?
-Lysosomal enzymes digest the particles, leaving a residual body
What is the fifth step in phagocytosis?
-Exocytosis of the vesicles removes indigestible and residual materials
What are natural killer cells?
-Nonphagocytic large granular lymphocytes
What are the functions of natural killer cells?
-Involved in tissue surveillance
-Attacks cells that lack "self" cell-surface receptors (induce apoptosis in cancer cells and virus-infected cells)
-Secrete potent chemicals that enhance inflammatory response
What are interferons?
-Family of immune modulating proteins (have slightly different physiology effects)
What is the function of interferons?
-Viral infected cells secrete interferons (IFNs) to "warn" neighboring cells (IFNs enter the neighboring cells -> produce proteins that block viral reproduction and degrade viral RNA: Activates NK cells)
Where are interferons secreted from?
-Lymphocytes (widespread immune mobilization effect: Activates macrophages)
What is the first stage of interferon activation?
-Virus enters the cell
What is the second stage of interferon activation?
-Interferon genes are switched on
What is the third stage of interferon activation?
-Cells produce interferon molecules
What is the fourth stage of interferon activation?
-Interferon binding stimulates cell to turn on gene for antiviral proteins
What is the last stage of interferon activation?
-Antiviral proteins block viral reproduction
What is the complement system?
-Blood proteins that circulate in inactive form
-Our cells contain complement activation inhibitors
What are the functions of the complement system?
-Major mechanism for destroying foreign substances
-Unleashes inflammatory chemicals that amplify all aspects of inflammatory response
-Kills bacteria and certain other cell types by cell lysis
-Enhances both the innate and adaptive defenses
What are the pathways to activate the complement system?
-Common terminal pathways initiated the enhances inflammation, promotes phagocytosis, which causes cell lysis
What are the three ways of complement activation?
What is the classic pathway of complement activation?
-Antibodies bind to the invading organism to complement components
What is the lectin pathway of complement activation?
-Lectin: produced by innate system to recognize foreign invaders
-When bound to foreign invaders, lectin can also bind and activate complement system
What is the alternative pathway of complement activation?
-Lack of inhibitors on microorganism's surface which allows the process to proceed
What is a fever?
-Abnormally high body temperature
-Systemic response to invading microorganisms
How is a fever caused?
-Leukocytes and macrophages exposed to foreign substances secretes pyrogens
-Pyrogens act on the body's thermostat in the hypothalamus, raising the body temperature
What are the benefits from a moderate fever?
-Causes liver and spleen to stop secreting iron and zinc (needed by microorganisms)
-Increased metabolic rate -> faster repair
What is the function of the inflammatory response?
-Triggered whenever the body tissues are injured
-Prevents spread of damaging agents
-Disposes of cell debris and pathogens
-Alerts adaptive immune system
-Sets the stage for repair
How is the inflammatory response started?
-Chemicals are released into the ECF by injured tissues, immune cells, and blood proteins
-Macrophages and epithelial cells of boundary tissues bear Toll-like receptors (TLRs)
-TLRs recognize specific classes of infecting microbes
-Activated TLRs trigger the release of cytokines that promote inflammation
What is phagocyte mobilization?
-Neutrophils lead and macrophages follow
-12 hours after leaving the bloodstream monocytes become macrophages (replace dying neutrophils and remain for clean up prior to repair)
What are the steps of phagocyte mobilization?
1). Leukocytosis: release of neutrophils from bone marrow in response to leukocytosis-induced factors from injured cells
2). Migration: Neutrophils cling to walls of capillaries in inflamed areas
3). Diapedesis of neutrophils
4). Chemotaxis: inflammatory chemicals (chemotactic agent) promotes positive chemotaxis of neutrophils
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