Presentation on theme: "Topic 6: Human Physiology"— Presentation transcript:
1 Topic 6: Human Physiology Fighting the Enemy Within!phagocytic leukocyteTopic 6.3Defense against the infectious diseaselymphocytesattackingcancer cell
2 What’s in your lunchbox? Why an immune system?Attack from outsidelots of organisms want you for lunch!animals are a tasty nutrient- & vitamin-packed mealcells are packages of macromoleculesno cell walltraded mobility for susceptibilityanimals must defend themselves against invadersvirusesHIV, flu, cold, measles, chicken pox, SARSbacteriapneumonia, meningitis, tuberculosisfungiyeast (“Athlete’s foot”…)protistsamoeba, Lyme disease, malariaAttack from insidedefend against abnormal body cells = cancersMmmmm,What’s in your lunchbox?
3 Avenues of attack Points of entry Routes of attack digestive system respiratory systemurogenital tractbreak in skinRoutes of attackcirculatory systemlymph system
4 Lymph system Production & transport of leukocytes Traps foreign invaderslymph vessels(intertwined amongst blood vessels)lymph node
13 Destroying cells gone bad! Natural Killer Cells perforate cellsrelease perforin proteininsert into membrane of target cellforms pore allowing fluid to flow into cellcell ruptures (lysis)apoptosisvesiclenatural killer cellperforincell membraneperforin punctures cell membranecell membranevirus-infected cell
14 Anti-microbial proteins Complement system~20 proteins circulating in blood plasmaattack bacterial & fungal cellsform a membrane attack complexperforate target cellapoptosisextracellular fluidcomplement proteins form cellular lesionplasma membrane of invading microbecomplement proteinsbacterial cell
15 Inflammatory response 1 Damage to tissue triggers local non-specific inflammatory responserelease histamines & prostaglandinscapillaries dilate, more permeable (leaky)increase blood supplydelivers WBC, RBC, platelets, clotting factorsfight pathogensclot formationaccounts for swelling, redness & heat of inflammation & infection
16 Inflammatory response 2 Reaction to tissue damagePin or splinterBlood clotswellingBacteriaChemicalalarm signalsPhagocytesBlood vessel
17 Fever When a local response is not enough systemic response to infectionactivated macrophages release interleukin-1 (IL-1)triggers hypothalamus in brain to readjust body thermostat to raise body temperaturehigher temperature helps defenseinhibits bacterial growthstimulates phagocytosisspeeds up repair of tissuescauses liver & spleen to store iron, reducing blood iron levelsbacteria need large amounts of iron to growCertain bacterial infections can induce an overwhelming systemic inflammatory response leading to a condition known as septic shock.Characterized by high fever and low blood pressure, septic shock is the most common cause of death in U.S. critical care units.Clearly, while local inflammation is an essential step toward healing, widespread inflammation can be devastating.
18 The Inflammatory Response 1- Tissue injury; release of chemical signals~ • histamine (basophils/mast cells): causes Step • prostaglandins: increases blood flow & vessel permeability2/3- Dilation and increased permeability of capillary~ • chemokines: secreted by blood vessel endothelial cells mediates phagocytotic migration of WBCs4- Phagocytosis of pathogens~ • fever & pyrogens: leukocyte-released molecules increase body temperature
19 3rd line: Acquired (active) Immunity Specific defenselymphocytesB lymphocytes (B cells)T lymphocytes (T cells)antibodiesimmunoglobulinsResponds to…antigensspecific pathogensspecific toxinsabnormal body cells (cancer)
20 How are invaders recognized: antigens proteins that serve as cellular name tagsforeign antigens cause response from WBCsviruses, bacteria, protozoa, parasitic worms, fungi, toxinsnon-pathogens: pollen & transplanted tissueB cells & T cells respond to different antigensB cells recognize intact antigenspathogens in blood & lymphT cells recognize antigen fragmentspathogens which have already infected cells“self”“foreign”
21 How are cells tagged with antigens Major histocompatibility (MHC) proteinsantigen glycoproteinsMHC I – on all nucleated cellsMHC II – on macrophages, B-Ly, activated T-LyMHC proteins constantly carry bits of cellular material from the cytosol to the cell surface“snapshot” of what is going on inside cellgive the surface of cells a unique label or “fingerprint”Major Histocompatability Complex (MHC): body cell surface antigens coded by a family of genesClass I MHC molecules: found on all nucleated cellsClass II MHC molecules: found on macrophages, B cells, and activated T cellsT cellMHC proteinsdisplaying self-antigens
22 Specific ImmunityLymphocyctes •pluripotent stem cells... • B Cells (bone marrow) • T Cells (thymus)Antibodies: antigen-binding immunoglobulin, produced by B cellsAntigen = a foreign molecule that elicits a response by lymphocytes (virus, bacteria, fungus, protozoa, parasitic worms)Antigen receptors = plasma membrane receptors on B and T cells
23 What else we’ll study? HIV & AIDS Human Immunodeficiency Virusvirus infects helper T cellshelper T cells don’t activate rest of immune system: T cells & B cellsalso destroy T cellsAcquired ImmunoDeficiency Syndromeinfections by opportunistic diseasesdeath usually from other infectionspneumonia, cancerTAttack!It’s too late…
24 To defend themselves against invaders! Animals are a tasty nutrient- & vitamin-packed meal !To defendthemselvesagainst invaders!What’s the point?
26 Immune system malfunctions Auto-immune diseasesimmune system attacks own molecules & cellslupusantibodies against many molecules released by normal breakdown of cellsrheumatoid arthritisantibodies causing damage to cartilage & bonediabetesbeta-islet cells of pancreas attacked & destroyedmultiple sclerosisT cells attack myelin sheath of brain & spinal cord nervesAllergiesover-reaction to environmental antigensallergens = proteins on pollen, dust mites, in animal salivastimulates release of histamine
27 Key attributes of immune system 4 attributes that characterize the immune system as a wholespecificityantigen-antibody specificitydiversityreact to millions of antigensmemoryrapid 2° responseability to distinguish self vs. non-selfmaturation & training process to reduce auto-immune disease
31 Induction of Immune Responses Primary immune response: lymphocyte proliferation and differentiation the 1st time the body is exposed to an antigenPlasma cells: antibody-producing effector B-cellsSecondary immune response: immune response if the individual is exposed to the same antigen at some later time~ Immunological memory