Chapter43TheBodysDefenses

1Chapter 43:The Bodys DefensesHow does your body protect you from invaders?2Immune System ReviewMicroorganism/MicrobePathogenAntibioticAntibodyAntigen 3Key Concepts3 Lines of DefenseInnate vs.Acquired immunityPhagocytes,Lymphocytes,Antibodies,etcHumoral vs.Cell-Mediated immunityDistinguishing self from non-selfTissue transplantationImmune Diseases/Disorders4Using HIV to treat Cancer?5What do you think?How does your body INITIALLY defend itself from invasion?(1st line specific or non?)What happens if the invader gets past the 1st line?(2nd line specific or nonspecific?)What about more serious infections?(3rd line)61st line Defense!Skin,mucus,cilia,saliva,acids,tears,oils,bacteria,coughing,sneezing,vomitingAntimicrobial proteins&Lysozymes 7Innate vs.Acquired ImmunityInnate Immunity:Present before exposure;since birth Includes natural bodily defenses,mothers milk,or casual exposure Broad-range capabilities,non-specific External defenses:skin,mucus membranes,tears Internal Phagocytic cells A.K.A.:“macrophages”;engulf invaders8Innate vs.Acquired ImmunityAcquired Immunity:Develops only after exposure Highly microbe-specific how?Employ lymphocytes&antibodies Involves both Humoral&Cell-Mediated responses9Innate Immunity:Your first line of defense10Phagocytic White Blood CellsRecognize&bind to carbohydrate markers on foreign cell membranes Triggers receptor-mediated endocytosis Engulf&digest pathogens via Phagocytosis11Types of White Blood CellsEosinophils:1.5%of WBCs;destroy large parasites extracellularlyNatural killer(NK)cells:trigger apoptosis in virus-infected cells&cancer cellsNeutrophils:60-70%of WBCs;engulf and destroy microbes at infected tissue;short livedMonocytes:5%of WBCs;develop into.Macrophages:“big eaters”enzymatically destroy microbes;can be found in spleen,lymph nodes,and other organs12Leukocyte vs.LymphocyteLeukocyte=White blood cells(WBCs)Lymphocyte=Specific type of WBC that mature and migrate through the lymphatic system and target specific antigens via antibodies,receptors and toxin release13The Inflammatory Response“Inflammation”=pain,swelling,fever,redness,itching,and pus14Causes of InflammationInjuriesExposure to microbes/pathogensExposure to foreign objects or chemicals(insect bites,stings,medications,etc)Exposure to allergens(pollen,pet dander,foods,etc)Rare:sunlight,temperature,self!15The Inflammatory Response3 Steps:1.Tissue damage=release of chemical signals Mast cells release chemicals known as Histamine&Prostaglandins that trigger inflammation2.Dilation increases permeability of capillaries Increased blood flow;leukocytes leak out to infected area Delivery of clotting factors&antimicrobial proteins3.Phagocytosis of pathogens WBCs engulf microbes or damaged tissue Fever:leukocyte-released chemicals increase body temperature16Acquired Immunity:Lymphocytes are the Key Defenders17Specific ImmunityAntigen:a foreign molecule that elicits a response from a lymphocyteLymphocyctes:WBCs that originate from stem cells in bone marrow B Cells(mature in bone marrow)T Cells(mature in thymus)Antibodies:antigen-binding immunoglobulin,produced by B cellsAntigen receptors:membrane receptors on B and T cells18Ch.43 Research:Humoral vs.Cell-mediated ResponsesB cells vs.T cellsMemory cellsClonal selectionAutoimmune disease19T cells vs.B cellsT cells:Mature in Thymus Target antigen fragments bound to MHC molecules on Infected Cells Part of Cell Mediated ResponseB cells:Mature in Bone Marrow Target in-tact Antigens Part of Humoral Response20Humoral vs.Cell-MediatedHumoral immunityB cell activationProduction of antibodiesDefend against intact antigens free in the lymph and blood plasma(bacteria,toxins,and viruses)21Humoral response:B cellsStimulated by an antigen-presenting macrophage(WBC w/a germ on it)Activates Helper T cellsT cells secrete cytokine chemicals that activate B cellsB cells differentiate into memory B cells and antibody-producing plasma cells 22CytokinesCytokine:Proteins secreted by phagocytic cells(macrophages,etc.)and T-helper cells Activate Lymphocytes(B&T cells)23Humoral Response:B cells activate.Plasma cells secrete antibodies.Antibodies attach to antigens.Antigens agglutinate(stick together)&get disposed.Macrophages phagocytose or lyse the cell.24Cell-mediated immunityT cells are activated.T cells bind to and/or lyse infected cells.Defend against cells infected with bacteria,viruses,fungi,protozoa,parasites,even cancer!Cell-Mediated25Cell-mediated Response1)Cell surface molecules expose antigens(foreign proteins).2)Cytotoxic T cell releases perforin,a protein that forms pores in the target cell membrane.causes cell lysis and exposes pathogens to circulating antibodies for disposal26Humoral ResponseCell Mediated ResponseIn Tact AntigensAntigens on Infected CellsB Cell ActivationT Cell ActivationSecrete antibodies that defend against pathogens&toxins in extracellular fluidDefend against infected cells,cancer and transplanted tissues27Clonal SelectionClonal selection:antigen-driven cloning of lymphocytesEffector cells:short-lived cells that combat the antigen initiallyMemory cells:long-lived cells that bear receptors for the antigen and activate upon subsequent exposure.28Active vs.Passive ImmunityActive:natural exposure to antigens causes ones own lymphocytes to activate and produce antibodies May also be acquired by ImmunizationsPassive:direct transfer of antibodies through placenta or mothers milk29 HIVHuman Immunodeficiency VirusCauses AIDS(Acquired Immune Deficiency Virus)HIV(a retrovirus)attacks helper T cells by binding with their cell receptor(CD4)This impacts both the Humoral and Cell Mediated responses 30Clonal Selection HypothesisEach lymphocyte bears one specific type of receptor.Receptor/antigen binding is required for cell activation.Activated lymphocytes divide and give rise to cells with identical receptors to the parent.This is how your immune system“remembers”a pathogen later!31Clonal Selection HypothesisFirst,those lymphocytes bearing receptors compatible to“self”tissues are destroyed(3)Second,those bearing receptors that match foreign antigens are activated then cloned(5/6)32Self/Nonself RecognitionSelf-tolerance:Capacity to distinguish self from non-self moleculesAutoimmune diseases:Failure of self-tolerance mechanisms Multiple sclerosis,lupus,rheumatoid arthritis,insulin-dependent diabetes mellitus,Crohns disease33Abnormal immune functionAllergies:hypersensitive responses to environmental antigens(allergens)causes dilation and blood vessel permeability Histamines are released from Mast cellsAutoimmune disease:multiple sclerosis Lupus rheumatoid arthritis insulin-dependent diabetes mellitusImmunodeficiency disease:SCIDS(bubble-boy)A.I.D.S.(HIV)34Cancer&the Immune SystemTumor cells are targeted by both Cytotoxic T cells and Natural Killer(NK)cellsHow might some tumors escape detection?35Treg research:Article ReviewWhat are“Regulatory T Cells”(Tregs)?What is their role in immunity?How might they be linked with cancer?Article:“Regulatory T cells and tumour immunity observations in mice and men”by Gallimore and Godkin,200736Major Histocompatibility ComplexAka:“MHC”Cell surface proteins that display fragments of antigens or processed proteins on the cell surfaceEpitope:region of antigen surfacerecognized by antibodies37Induction of Immune ResponsesPrimary immune response:lymphocyte proliferation and differentiation the 1st time the body is exposed to an antigenPlasma cells:antibody-producing B-cellsSecondary immune response:immune response if the individual is exposed to the same antigen at a later time Immunological memory38Types of ImmunoglobinsIgM:1st to circulate;indicates infection;too large to cross placentaIgG:most abundant;crosses walls of blood vessels and placenta;protects against bacteria,viruses,&toxins;activates complementIgA:produced by cells in mucous membranes;prevent attachment of viruses/bacteria to epithelial surfaces;also found in saliva,tears,and perspirationIgE:very large;small quantity;releases histamines-allergic reaction39Antibody-Mediated Antigen DisposalNeutralization(opsonization):antibody binds to and blocks antigen activityAgglutination:antigen clumpingPrecipitation:cross-linking of soluble antigensComplement fixation:lyses viruses and pathogenic cells&activates cell surface proteins to break down the cell40Immunity in Health&DiseaseActive immunity:natural:conferred immunity by recovering from disease artificial:immunization and vaccination;produces a primary responsePassive immunity:transfer of immunity from one individual to another natural:mother to fetus;breast milk artificial:rabies antibodiesABO&Rh blood groups(antigen presence)