Presentation on theme: "Ch. 43 The Immune System Objectives"— Presentation transcript:
1 Ch. 43 The Immune System Objectives LO 2.28 The student is able to use representations or models to analyze quantitatively and qualitatively the effects of disruptions to dynamic homeostasis in biological systems.LO 2.29 The student can create representations and models to describe immune responses.LO 2.30 The student can create representations or models to describe nonspecific immune defenses in plants and animals.LO 2.34 The student is able to describe the role of programmed cell death in development and differentiation, the reuse of molecules, and the maintenance of dynamic homeostasis.
2 Pathogens (such as bacteria, fungi, and viruses) OverviewInnate Immunity – defenses are activated immediately upon infection; same response for all pathogens.Adaptive (Acquired) Immunity – defenses based on recognition of the pathogen.Pathogens (such as bacteria, fungi, and viruses)INNATE IMMUNITY (all animals)• Rapid responseRecognition of traits shared by broad ranges of pathogens, using a small set of receptors•Recognition of traits specific to particular pathogens, using a vast array of receptors• Slower responseBarrier defenses:Skin Mucous membranes SecretionsInternal defenses:Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory responseHumoral response:Antibodies defend against infection in body fluids.Cell-mediated response:Cytotoxic cells defend against infection in body cells.ADAPTIVE IMMUNITY (vertebrates only)
3 Invertebrates Exoskeleton (chitin) Ch In Innate Immunity, Recognition and Response Rely on Traits Common to Groups of PathogensInvertebratesExoskeleton (chitin)Chitin-based barriers and lysozymes (break down bacterial walls) in intestinesHemocytesPhagocytosisChemicalsAntimicrobial peptides (disrupt fungi and bacterial plasma membranes)Specialized recognition proteinsPathogenPHAGOCYTIC CELLVacuoleLysosome containing enzymes
4 Vertebrates Barrier defenses Skin Cilia: sweep mucus and any entrapped microbes upward, preventing the microbes from entering the lungsLysozymes inMucus – traps microbesSalivaTearsAcidicSweatStomach juices
5 Cellular Innate Defenses Phagocytosis after Toll-like receptor recognizes pathogenNeutrophils: circulate in bloodMacrophages: live in cells/organs (spleen)Dendritic cells: tissue in contact with environment (skin)Eosinophils: beneath mucosal surfaces; multicellular pathogens.Natural Killer Cells: secrete chemical when they come in contact with a pathogenAntimicrobial Peptides and ProteinsInterferonsMade by virally infected cells to warn surrounding cells.
6 Inflammatory Response Histamine is released by mast cells in response to tissue damageTrigger dilation and increased permeability of nearby capillariesIncreased blood flow delivers clotting factors to the injury (marks beginning of repair process/blocks spread of microbes)Cytokines from macrophages/neutrophils promote blood flow causing redness and increased temp in the area.Pus—the accumulation of dead phagocytic cells and fluid leaked from capillariesPathogenSplinterMast cellMacro- phageCapillaryRed blood cellsNeutrophilSignaling moleculesMovement of fluidPhagocytosis
7 43.2 In Adaptive Immunity, Receptors Provide Pathogen-Specific Recognition Pathogens have antigens that trigger lymphocytic responses.B cellsBinding of Y shaped antigen receptor on membrane to antigen causing it to secrete soluble receptors called antibodies.T cellsSingle rod shaped antigen receptor only binds to already infected host cells that display the antigen.AntibodyAntigen receptorB cellAntigenEpitopePathogen(a) B cell antigen receptors and antibodiesAntibody CAntibody BAntibody A(b) Antigen receptor specificityDisplayed antigen fragmentMHC moleculeAntigen fragmentPathogenHost cellT cellT cell antigen receptor(a) Antigen recognition by a T cell
8 Characteristics of Adaptive Immunity Immense diversity of lymphocytes and receptors.> 1 million different B cell antigen receptors; 10 million different T cell antigens; each cell carries a specific set of theseSelf-tolerance.Lymphocytes are tested; any with “self” receptors go through apoptosis.Once recognized, increasing the number of specific lymphocytes for an antigen.Active lymphocyte divides by mitosis making cloned effector cells (begin fighting immediately; B=plasma cells; T= helper T cells and cytotoxic T cells) and memory cells (long lived cells that activate if antigen enters the body again)Stronger and quicker response to previously encountered antigens.Memory cells
9 Cell- mediated immunity 43.3 Adaptive Immunity Defends Against Infection of Body Fluids and Body CellsCell-Mediated Immune Response (attacks infected body cells)Active helper T cells secrete cytokines which activate cytotoxic T cells.Cytotoxic T cells bind to infected host cellsSecretes proteins that disrupt membrane integrity and trigger apoptosis.Once destroyed, antibodies attach to antigens from within the host cell.Antigen- presenting cellPathogenAntigen fragmentClass II MHC moleculeAccessory proteinAntigen receptorHelper T cellCytokinesCell- mediated immunityCytotoxic T cell21Cytotoxic T cell312Accessory proteinClass I MHC moleculeInfected cellAntigen receptorAntigen fragmentPerforinPoreGran- zymesReleased cytotoxic T cellDying infected cell
12 Humoral Immune Response (attacks pathogen) Helper T cells activate B cells.B cells divide into memory or plasma cells.Plasma cells give secrete 2,000 antibodies/sec!Antibodies:Prevent the pathogen from infecting cells (neutralization)Increase phagocytosis due to easy recognition (opsonization)Complement system of proteins opens a pore in the pathogen causing water to rush in the pathogen to lyse.Pathogen312Antigen-presenting cellAntigen fragmentClass II MHC moleculeAntigen receptorAccessory proteinHelper T cellB cellCytokinesActivated helper T cellMemory B cellsPlasma cellsSecreted antibodiesOpsonizationNeutralizationAntibodyVirusBacteriumMacrophageActivation of complement system and pore formationComplement proteinsFormation of membrane attack complexFlow of water and ionsPoreAntigenForeign cell
13 Humoral (antibody-mediated) immune response Cell-mediated immune responseAntigen (1st exposure)Engulfed byAntigen- presenting cellHelper T cellMemory helper T cellsAntigen (2nd exposure)B cellPlasma cellsSecreted antibodiesDefend against extracellular pathogensMemory B cellsMemory cytotoxic T cellsActive cytotoxic T cellsDefend against intracellular pathogens and cancerCytotoxic T cellKeyStimulatesGives rise to
14 Active and Passive Immunization Active (cell mediated and humoral responses)Can be induced by vaccinations – weakened, killed, or parts of pathogens to – to create memory cells and can lead to immunization.Passive (passed on from mother to child for first few months of life)Injection of antibodies from an immune animal to a non-immune animal.
15 Immune RejectionCells from another person’s body can be recognized as foreign due to different carbohydrate found on the cell membranes, causing an immune response.Blood groups (ABO)Tissue and Organ Transplant
16 43.4 Disruptions in Immune System Function Can Elicit or Exacerbate Disease AllergiesExaggerated responses to allergens.Autoimmune diseasesImmune system does not recognize “self-cells”LupusArthritisDiabetesMS
17 Immunodeficiency Diseases Inborn immunodeficiency results from hereditary or developmental defects that prevent proper functioning of innate, humoral, and/or cell-mediated defensesAcquired immunodeficiency develops later in life and results from exposure to chemical and biological agentsAcquired immunodeficiency syndrome (AIDS) is caused by a virus
18 Evolutionary Adaptations of Pathogens Antigenic VariationChanges its antigens so the host does not recognize itEx: FluLatencyInactive state which does not trigger an immune response (lysogenic cycle).Attacking the Immune System ItselfHIV – attacks helper T cells preventing both cell mediated and humoral responses to infections.
19 Cancer and ImmunityThe frequency of certain cancers increases when adaptive immunity is impaired20% of all human cancers involve virusesThe immune system can act as a defense against viruses that cause cancer and cancer cells that harbor virusesIn 2006, a vaccine was released that acts against human papillomavirus (HPV), a virus associated with cervical cancer.