Immune System

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What It’s All About – the BASICS

• Defend the body against pathogens• Recognize self from non-self • Specific and Non-specific

“Bottom line”:

Fight infection through the production of cells that inactivate foreign substances/cells

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Protection

• Pathogens– Infectious disease– Toxic– Reproduce in the host– GERMS

• Koch’s postulate

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4 ways of getting sick

• Contact an infected person directly

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4 ways of getting sick

• Contact an infected person INdirectly

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4 ways of getting sick

• Eat infected food or drink infected water

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4 ways of getting sick• Get bitten by an infected animal

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Bubonic Plague

Bubonic plague is an infectious disease, circulating mainly among small rodents and their fleas. Without treatment, the bubonic plague kills about two thirds of infected humans within 4 days. Swollen lymph glands are typical symptoms of the plague. During the 14th century, 25 million people in Europe were belived to have died (around 40% of the entire population). 9

Immune System Anatomy

• Lymphatic System–Lymph (fluid with WBCs)–Lymph nodes (store WBCs)–Tonsils, thymus, spleen, appendix, red

bone marrow, adenoids

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Line up the Troops• First line of defense is non-specific

– Blocks anything from entering body system

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First Line of Defense Examples

• Skin: wall that blocks pathogens• Sweat: acidic, salty, contains enzymes• Mucus: coats openings to body• Tears: wash out pathogens entering eye

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If that didn’t work….

• Second line of defense: Inflammatory ResponseWhen the pathogen enters the body

– Injured cells release HISTAMINE• Capillaries expand so blood flow increases• Fluid leaks out into space between cells

– Swelling, redness, pain, heat

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SPECIFIC DEFENSEIMMUNE RESPONSE

– Specific for pathogen– Most effective if you’ve been infected

before– Through entire body– Triggered by substance in pathogen =

antigen– Can be defense in body fluids (humoral) OR

defense against abnormal cells or pathogens (cell-mediated)

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Cells InvolvedWhite Blood cells = LEUKOCYTES

They are made in the bone marrow

Some develop in bone marrow, others in the thymus

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Cells Specifics

Non-specific:

Phagocytes: engulf (eat) and digest pathogens

Macrophages are the biggest

Specific: Lymphocytes: B-cells and T-cells

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Humoral Immunity – Immunity against pathogens in body fluids

Some B cells recognize specific pathogen• B cells mature in Bone marrow• Antibodies from B-cells • Some B cells remember specific antigens &

will produce antibodies whenever the pathogen reappears (memory cells)

• Antibodies:– Attach to antigen and attract macrophages

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B cell immune response10 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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tested by B cells(in blood & lymph)

Lymphocytes: B-cell

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Cell-Mediated Immunity

• Cells directly attack and destroy Ag (antigen)– Cancer cells, infected body cells, invading cells

• T cells involved– Born in bone marrow but mature in Thymus– 3 types: killer, helper, suppressor

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T cells

• Killer T cells– Attack Ag (puncture cell membrane)

• Helper T cells (aka T4)– Stimulate Killer Ts to divide, stimulate B cells to

divide and release Antibodies

• Suppressor T cells– Stop the activity of other T cells

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T cell response

stimulateB cells &antibodies

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killerT cell

activatekiller T cells

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infected cell

helperT cell

helperT cell

helperT cell

helperT cell

helperT cell

activatedmacrophage

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Lymphocytes From Stem Cells

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Lymphocytes: T-cell

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Memory CellsPrimary response: new pathogen, new response (5-10 days until max production of B and T cells)

Secondary Response: same pathogen, old response (1-2 days, so you don’t even get sick!)

Memory cells can last your entire life!!

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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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Immune response

free antigens in blood antigens on infected cells

humoral response cellular response

B cells T cells

macrophages(APC)

helperT cells

plasmaB cells

memoryB cells

memoryT cells

cytotoxicT cells

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skinskinpathogen invasionantigenexposure

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HIV and AIDS

• HIV attacks T4 cells (Helper T cells)• Body can’t defend against any Ags!• Known as an STD: transported in semen, blood,

breast milk

• Once T4 count is so low that body can’t fight disease, we say the person has AIDS

• Takes about 10 years to develop AIDS

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AIDS Infection

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Huge Outbreak in Africa

African Children Orphaned by AIDS31

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Allergies

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Allergies

• Histamine released even though antigen is harmless

• If blood vessels dilate too much: ANAPHYLACTIC SHOCK

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Autoimmune Disorders

• Immune system attack SELF cells

• Multiple Sclerosis: T cells destroy nerve cells

• Maybe Type 1 Diabetes is attack on pancreas

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Multiple Sclerosis

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