AP Biology

Immune / LymphaticSystem

lymphocytesattackingcancer cell

phagocytic leukocyte

lymphsystem

Fighting theEnemy Within!

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Objectives 3 lines of defense Non-specific vs specific defense Active vs passive immunity Antibody structure and function Humoral vs cell-mediated responses

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Agents of disease (PATHOGENS) Viruses

Bacteria

Protists

Fungi

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How do diseases spread Physical contact Contaminated food and water Infected animals/ VECTORS

Insects/ arachnids

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Types of diseases Viral – measles, mumps, HIV, flu, cold,

chickenpox Bacterial – strep throat, cholera,

botulism, bubonic plague, staph infection, Lyme’s disease

Protist – dysentery, malaria, African sleeping sickness

Fungal – athletes foot, ringworm, Candida, thrush

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Avenues of attack Points of entry

digestive system respiratory system urogenital tract break in skin

Routes of attack circulatory system lymph system

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Non-specific Defense1. 1st: Barriers (skin/ mucous membranes)

2. 2nd: Non-specific patrol (phagocytic WBC’s)

3. 2nd: Immune Response

4. 2nd: Fever

1st Line of Defense

2nd Line of Defense

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Non-specific Lines of defense 1st line: Barriers

broad, external defense “walls & moats”

skin & mucus membranes 2nd line: Non-specific patrol

broad, internal defense “patrolling soldiers”

leukocytes = phagocytic WBC macrophages

Bacteria & insectsinherit resistance.

Vertebratesacquire immunity!

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1st and 2nd lines of defense are NON-SPECIFIC

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1st line: External defense Physical & chemical

defenses non-specific defense

external barrier epithelial cells &

mucus membranes skin respiratory system digestive system uro-genital tract

Lining of trachea: ciliated cells & mucus secreting cells

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1st line: Chemical barriers on epithelium Skin & mucous membrane secretions

sweat pH 3-5

tears washing action

mucus traps microbes

saliva anti-bacterial enzymes

stomach acid pH 2

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2nd line: Internal, broad range patrol leukocytesleukocytes Innate, general defense

rapid response

Patrolling cells & proteins attack invaders that

penetrate body’s outer barriers leukocytes

phagocytic white blood cells

Interferons complement system

anti-microbial proteins

inflammatory response

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Interferons Interferons are proteins made and

released by host cells in response to the presence of pathogens such as viruses, bacteria, parasites or tumor cells.

Interferon therapy (IF) can be helpful in alleviating symptoms of viral disease but DO NOT eradicate the virus.

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Phagocytes = eating cells

yeastmacrophage

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2nd line: Inflammatory Response http://www.sumanasinc.com/webconten

t/animations/content/inflammatory.html

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Inflammatory response Triggered by damage to

tissue triggers local non-specific

inflammatory response release histamines

capillaries dilate, more permeable (leaky)

increase blood supply delivers WBC, RBC, platelets,

clotting factors fight pathogens clot formation accounts for swelling, redness &

heat of inflammation & infection

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Inflammatory response

Bacteria

Blood vessel

Chemicalalarm signals

Pin or splinterBlood clot

Phagocytes

swelling

Reaction to tissue damage

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2nd line: Fever When a local response is not enough

higher temperature helps defense inhibits bacterial growth Increases heart rate – WBC’s can get to infection faster speeds up repair of tissues causes liver & spleen to store

iron, reducing blood iron levels bacteria need large amounts

of iron to grow

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Non-specific Defense Barriers – 1st Line Non-specific patrol – 2nd Line Immune Response – 2nd Line Fever – 2nd Line

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When this is not enough,Our third line of defense kicks in

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Specific Line of defense 3rd line: Immune response

specific, acquired immunity “elite trained units”

Foreign invader (called an antigen) triggers this response

Cells involved Lymphocytes

B cells Humoral response

T cells Cell-mediated response

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Immune Response http://highered.mcgraw-hill.com/sites/0

072507470/student_view0/chapter22/animation__the_immune_response.html

AP Biology“self” “foreign”

How are invaders recognized: antigens Antigens

proteins that serve as cellular name tags foreign antigens cause response from WBCs

viruses, bacteria, protozoa, parasitic worms, fungi, toxins non-pathogens: pollen & transplanted tissue

B cells & T cells respond to different antigens B cells recognize intact antigens

pathogens in blood & lymph T cells recognize antigen fragments

pathogens which have already infected cells

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Key attributes of a good immune system

4 attributes that characterize the immune system as a whole specificity

antigen-antibody specificity diversity

react to millions of antigens memory

rapid 2° response ability to distinguish self vs. non-self

maturation & training process to reduce auto-immune disease

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B cells Humoral response = “in fluid”

defense against attackers circulating freely in blood & lymph

Specific response produce specific antibodies

against specific antigen Types of B cells

plasma cells immediate production of antibodies rapid response, short term release

memory cells Stay in body Recognizes invader on future infections long term immunity

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B cell immune responsetested by

B cells(in blood & lymph)

10 to 17 days for full response

invader(foreign antigen) B cells + antibodies

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recognition

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clone1000s of clone cellsY

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plasma cellsrelease antibodies

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memory cells“reserves”

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Ycapturedinvaders

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Antibodies

Proteins that bind to a specific antigen multi-chain proteins produced by B cells binding region matches molecular shape of antigens each antibody is unique & specific

millions of antibodies respond to millions of foreign antigens

tagging “handcuffs” “this is foreign…gotcha!”

each B cell has ~100,000

antigen receptors

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antigenantigen-binding site on antibody

variable binding region

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Structure of antibodies

light chains

antigen-bindingsite

heavy chains

antigen-bindingsite

lightchain

lightchain

heavychains

B cellmembrane

variable region

antigen-binding siteY

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How antibodies work

macrophageeating tagged invaders

invading pathogens tagged with antibodiesY

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Huh? Antibodies = proteins (Y-shaped)…

DEFEND you against pathogens. Your body makes these in response to

antigens

Antigens = proteins that GENerate the immune response (are bound up by antibodies)

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1° vs 2° response to disease Memory B cells allow a rapid, amplified

response with future exposure to pathogen

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Vaccinations Immune system exposed

to harmless version of pathogen triggers active immunity stimulates immune system to produce

antibodies to invader rapid response if

future exposure

Most successful against viral diseases

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Obtaining antibodies from another individual

Maternal immunity antibodies pass from mother to baby across

placenta or in mother’s milk critical role of breastfeeding in infant health

mother is creating antibodies against pathogens baby is being exposed to

Injection injection of antibodies short-term immunity

Passive immunity

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What if the attacker gets past the B cells in the blood & actually infects some of your cells?

You need trained assassins to kill off these infected cells!

Attackof the

Killer T cells!

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T cells Cell-mediated response

immune response to infected cells viruses, bacteria & parasites (pathogens)

within cells defense against “non-self” cells

cancer & transplant cells

Types of T cells helper T cells

alerts immune system killer (cytotoxic) T cells

attack infected body cells

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How do T cells know a cell is infected Infected cells digest pathogens & MHC

proteins bind & carry pieces to cell surface antigen presenting cells (APC) alerts Helper T cells

MHC proteins displaying foreign antigens

infectedcell

T cellantigen receptors

T cellWANTED

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T cell response

stimulateB cells &

antibodies

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killerT cell

activatekiller T cells

orinterleukin 1

interleukin 2

interleukin 2

infected cell

helperT cell

helperT cell

helperT cell

helperT cell

helperT cell

activatedmacrophage

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HIV & AIDS Human Immunodeficiency Virus

virus infects helper T cells helper T cells don’t activate rest of

immune system: T cells & B cells also destroy T cells

Acquired ImmunoDeficiency Syndrome infections by opportunistic

diseases death usually from secondary

infections pneumonia, cancer

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Immune system malfunctions Auto-immune diseases

immune system attacks own molecules & cells lupus

antibodies against many molecules released by normal breakdown of cells

rheumatoid arthritis antibodies causing damage to cartilage & bone

diabetes beta-islet cells of pancreas attacked & destroyed

multiple sclerosis T cells attack myelin sheath of brain & spinal cord nerves

Allergies over-reaction to environmental antigens

allergens = proteins on pollen, dust mites, in animal saliva

stimulates release of histamine

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AP Biology

Immunity The 3 lines of defense Non-specific vs. specific Acquired vs. passive immunity Humoral vs. Cell-mediated response