The Immune System

Nonspecific and Specific Defense

You do not need to write down anything in blue.

What is a pathogen?• Pathogen:Pathogen: disease causing agentdisease causing agent

• Harmful to living thingsHarmful to living things

Check out this slow motion sneeze!

http://www.youtube.com/watch?v=e2QAGVMlns4

Examples of Pathogens include

• BacteriaBacteria

• VirusesViruses

• Parasites, Parasites, like fungi, like fungi, protists, & wormsprotists, & worms

• SoilSoil• WaterWater• Infected animalsInfected animals

• FoodFood• Animal BitesAnimal Bites

– This includes mosquitoes (West Nile Virus), ticks This includes mosquitoes (West Nile Virus), ticks (Lyme Disease), fleas (Bubonic plague), flies (Lyme Disease), fleas (Bubonic plague), flies (various infections)(various infections)

• Person-to-person contactPerson-to-person contact

How are Pathogens How are Pathogens Spread?Spread?

Q: How do bacteria cause damage to host cells?

A: By releasing poisonous substances called toxins.

• Did you know?…the Tetanus bacteria is found in soil and one drop of the toxin, the size of a period, can kill 30 people.

These images are of two men undergoing an extreme muscle

spasm caused by toxins produced by tetanus bacteria.

The Immune SystemThe Immune System

Immune System:Immune System: body system body system that fights off invading pathogensthat fights off invading pathogens

Two types of defense:Two types of defense:• Nonspecific DefenseNonspecific Defense• Specific DefenseSpecific Defense

11stst line of line of Non-Specific Non-Specific

DefenseDefense Skin: A physical barrier to A physical barrier to

pathogens.pathogens.• Any break in the skin allows Any break in the skin allows

entry.entry.• Releases sweat, oils, and Releases sweat, oils, and

waxes that contain waxes that contain chemicals toxic to bacteriachemicals toxic to bacteria..

Mucous membranes: Tissues that line internal body Tissues that line internal body surfaces that are in contact surfaces that are in contact with the environment.with the environment.• Mucous: Sticky fluid that Sticky fluid that

traps pathogens.traps pathogens.

1st line of Defense:Types of Non-specific

Defense Stomach: Has acid that Has acid that

destroys potential pathogens destroys potential pathogens that are swallowedthat are swallowed

Phagocytes: WBC’s that WBC’s that ingest (eat) pathogensingest (eat) pathogens• Macrophages: Ingest and Ingest and

destroy pathogens.destroy pathogens.• Neutrophils: Ingest Ingest

pathogens, then secrete pathogens, then secrete deadly toxic chemicals to deadly toxic chemicals to kill themkill them

• Short video clip on phagocytes: Short video clip on phagocytes: http://www.youtube.com/watch?v=CEOV-SFTlpY. .

Phagocytes and their relatives

Macrophage

Neutrophils

11stst line of Defense: line of Defense:Types of Non-specific Types of Non-specific

DefenseDefense Moderate Fevers (< 103O F):

Inhibit growth of pathogens and recruit macrophages

Inflammation: Reaction to tissue damage. Phagocytes consume foreign substances. (Symptoms: swollen, redness, heat, pain)

InflammationFigure 24.2

Tissue injury; release of chemical signals such ashistamine.

1 2 3Dilation and increased leakiness of local blood vessels; migration of phagocytes to the area.

Phagocytes (macrophages andneutrophils) consume bacteria and cell debris; tissue heals.

PinSkin surface

Bacteria

Chemicalsignals

WBC

Swelling

Phagocytes andfluid moveinto area

Phagocytes

Specific Defense: The Immune System

Organs of the Immune System:• Bone Marrow:

makes WBC• Thymus gland:

where T cells mature• Lymph nodes:

contain lots of WBC• Spleen: removes

pathogens from blood

The Immune System involves many The Immune System involves many types of White Blood Cells types of White Blood Cells (aka (aka

Leukocytes / WBCs).Leukocytes / WBCs).

Here are a few types:Here are a few types:B lymphocytes: Secrete antibodies.

Antibodies: Y-shaped molecules that grab and block certain

pathogens.

T lymphocytes: Help stimulate an immune response.

You can call them B cells

and T cells for short!

Specific Defense: Recognizing Specific Defense: Recognizing PathogensPathogens

Immune Response:: your wbcs attack somethingyour wbcs attack something Antigen: anything that causes a responseanything that causes a response

Recognition: Recognition: – Lymphocytes have receptor proteins all over them.Lymphocytes have receptor proteins all over them.– Receptor proteins recognize and bind to antigens Receptor proteins recognize and bind to antigens

that match the receptor.that match the receptor.

Immune Response gets stronger over time

Primary Immune Response: 1st time a certain pathogen is encountered by the body• After infection is fought, some B and T

cells stay alive for years as memory cells.• Memory cells can divide to fight

pathogens that they “remember” if they ever meet again.

Secondary Immune Response: a later exposure to the same pathogen

• Response is faster and stronger due to memory cells.

Draw this graph!