AP Biology 2006-2007

“Fighting the Enemy Within”

Immune System

lymphocytesattackingcancer cell

phagocytic leukocyte

lymphsystem

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Avenues of attack Points of entry

digestive system – mouth – saliva/acid respiratory system – nose – hairs/mucus urinary system – urethra (shorter in females) genitals break in skin – cut eyes

Pathways for attack circulatory system lymph system

How pathogens move around your body

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Why do we need an immune system? Attack from the outside & inside

cells are packages of proteins, carbohydrates & fats no cell wall – plasma membrane – semi permeable

organisms must defend themselves against (pathogens) invaders viruses – NOT LIVING

HIV, flu, cold, measles, chicken pox, SARS bacteria

pneumonia, meningitis, tuberculosis, strep throat fungi

yeast, ringworm, athlete’s foot protists

amoeba (disentary) , Lyme disease, malaria cancer cells – come from within

abnormal body cells – “starve” healthy cells

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How are invaders recognized? Antigens

chemical name tags on the surface of every cell – Protein

“self” vs. “invader” – ALL BASED ON SHAPE

disease-causingbacteria

disease-causingvirus

one of yourown cells

antigens say:“I belong here”

antigens say:“I am an invader”

antigens say:“I am an invader”

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1st line: Physical Barriers

non-specific defense external barriers

skin & mucus membranes excretions

sweat stomach acid tears mucus saliva

“lick your wounds”

Lining of trachea:

ciliated cells & mucus secreting cells

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2nd: Generalist, broad range patrols White blood cells

attack invaders that get through the skin recognize invader by reading antigen

surface name tag – BASED ON SHAPE

phagocyte cells macrophages “big eaters” “eat” like amebas

engulf (endocytosis, then fuse with lysosome,and finally exocytosis)

Macrophage “eating” bacteria

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histaminesincreases blood flow (red and warm)brings more white blood cells to fight bacteria

(pus)brings more red blood cells & clotting factors to

repair

Why do injuries swell?

Inflammation - injured cells release chemical signals

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Fever

When a local response is not enough full body response to infection raises body temperature – 37 C or 98.6 F TOO high – dangerous – remember

enzymes???? higher temperature helps in defense

slows growth and metabolism of pathogens helps macrophages speeds up repair of tissues

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3rd line: Lymphocytes Specific defense

responds to specific invaders recognizes specific

foreign antigens white blood cells

B cells & antibodiesT cells

B cell

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B cells & antibodies ACTIVE IMMUNITY B cells

white blood cells that attack invaders in blood

mature in Bone marrow Patrolling B cells

make antibodies against invader immediately

Memory B cells remembers invader can make antibodies quickly the next time

protects you from getting disease more than once

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Proteins made by B cells that tag invaders in the blood so macrophages can eat them tag says “this is an invader” gotcha!

biological “handcuffs” antibody attaches to antigen of invader –

they “FIT”

Antibodies

macrophageeating tagged invaders

invading germs tagged with antibodies Y

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B cells releasing antibodies

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Y Y

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Y

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B cells immune responseinvader

(foreign antigen)

Y

Y

Y

Y

B cellsY

YY

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Y

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Y

Y

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Y

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“reserves”

memory B cells

Y

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Y

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Y

Y

B cellsrelease

antibodiespatrol blood

forever

recognition

10 to 17 days

YY

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YY YY

Y

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Y

Antibody “fits” with antigen

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Vaccinations Exposure to harmless version (“dead”,

weakened, or part) of a pathogen (“germ”) stimulates immune system to produce

antibodies to invader - ACTIVE IMMUNITY rapid response if future exposure

Most successful against viral diseases

Ex: flu, chicken pox, HPV,MMR, swine flu, whooping

cough, polio, small pox

Jonas Salk Developed first vaccine

against polio

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Vaccinations – Active Immunity advantage

don’t get illness long term immunity - produce antibodies for life works against many viruses & bacteria

disadvantage not possible against all invaders

Breastfeeding - Passive Immunity mother’s milk gives baby antibodies & keeps

baby healthy

Protecting you from disease

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Curing you of disease Antibiotics = medicine

advantage kill bacteria that have successfully

invaded you make you well after being sick

disadvantage use only after sick only good against bacteria possible development of

resistance by bacteria (if don’t use correctly) – ALWAYS TAKE THE ENTIRE Rx

can get sick again

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Diseases of the immune system HIV: Human Immunodeficiency Virus

infects helper T cells helper T cells can’t activate rest of

immune system body doesn’t hear the alarm

AIDS:Acquired ImmunoDeficiency Syndrome immune system is weakened infections by other diseases death from other invading

diseases or cancer

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Immune system malfunctions Auto-immune diseases

immune system attacks own cells lupus

antibodies attack many different body cells

rheumatoid arthritis antibodies causing damage to

cartilage & bone

diabetes insulin-making cells of pancreas

attacked & destroyed

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

nerves fatal

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Immune system malfunctions Allergies

produce histamines over-reaction to harmless antigens

allergens proteins on pollenproteins from dust mitesproteins in animal saliva

body mistakenly thinks they are harmfulattackers (antigens)