The Immune System

Pathogens• Defined: microorganisms

that cause disease– Viruses: turn cells into

virus making factories

Pathogens• Defined: microorganisms

that cause disease– Viruses: turn cells into

virus making factories– Bacteria: prokaryotes

that can release toxic chemicals

Pathogens• Defined: microorganisms

that cause disease– Viruses: turn cells into

virus making factories– Bacteria: prokaryotes

that can release toxic chemicals

– Fungi: pierce cells and absorb the nutrients

Pathogens• Defined: microorganisms

that cause disease– Viruses: turn cells into

virus making factories– Bacteria: prokaryotes

that can release toxic chemicals

– Fungi: pierce cells and absorb the nutrients

– Protozoans: single cells protista (eukaryotes)

Plasmodium causes malaria

Pathogens• Defined: microorganisms

that cause disease– Viruses: turn cells into

virus making factories– Bacteria: prokaryotes

that can release toxic chemicals

– Fungi: pierce cells and absorb the nutrients

– Protozoans: single cells. Protists (eukaryotes)

– Parasites: grow and feed on a host

tapeworms

Transmission• Some carried by wind,

water, direct contact, indirect contact…

• Vectors: organism that carries a pathogen

Examples:1) Malaria – mosquitos

carry the protozoan2) Black Death – carried by

fleas of mice3) West Nile Virus – carried

by birds, but spread by mosquitoes

The Skin• 1st line of defense: physical barrier• Oils & sweat destroy some pathogens

–Some pathogens burst…some shrivel

Skin

bacteria bacteria

Mucus Membranes

• Coat the openings of the body– Nose, mouth, ears, eyes, genitals, anus

• Lined with cilia & sticky fluids to trap pathogens

White Blood Cells

• Job: Search & destroy

YouTube Clip: Types of White Blood Cells (phagocytes) from the BBC

YouTube Clip: Types of White Blood Cells (lymphocytes) from the BBC

White Blood Cells

• Job: Search & destroy• Type 1: Phagocytes

– surround & engulf invaders by phagocytosis

YouTube Clip: Types of White Blood Cells (phagocytes) from the BBC

YouTube Clip: Types of White Blood Cells (lymphocytes) from the BBC

White Blood Cells

• Job: Search & destroy• Type 1: Phagocytes

– surround & engulf invaders by phagocytosis• Type 2: Lymphocytes

– create antibodies & destroy infected body cells

YouTube Clip: Types of White Blood Cells (phagocytes) from the BBC

YouTube Clip: Types of White Blood Cells (lymphocytes) from the BBC

Blood stream

Defense Proteins• Antibodies

– Created & released by lymphocytes

– Attach to antigens (like handcuffs)

lymphocyte

antibody

YYY

YYY

Y

Y

Defense Proteins• Antibodies

– Created & released by lymphocytes

– Attach to antigens (like handcuffs)

• How do they kill?1) Causes pathogens to

clump2) Weakens the cell

membrane of the pathogen

B

B

BYY Y

Y

Y

Y

B CELLS MAKE ANTIBODIES

ANTIBODIES ATTACH TO ANTIGENS OF THE PATHOGEN

PHAGOCYTE DESTROYS PATHOGENS

YY

Y

YY

ANTIBODIES CAUSE THE PATHOGENS TO CLUMP TOGETHER

B

B

BBlood Stream

Y

Y

Y

Y

Y

Y YY

YY

YY

phagocyte

• Interferon1) Cell becomes

infected by virus2) Infected cell

sends interferon to healthy neighbors

3) Interferon causes healthy cell to create defense enzymes

4) Healthy cell able to fight virus

Defense ProteinsVirus RNA

New virus

New virus

New virusInterferon

virus

Infected!

InterferonInterferon

New virus

New virus

Not Infected!

Vaccination• Prevents infections (not

a cure)• Vaccination process

– Weakened pathogen is injected

– Immune system produces…• Antibodies to fight

the weakened pathogen

• Memory cells for future infections

• Goal: Speed up immune response if you encounter the actual virus

Review

1) Which part of our immune system coats the openings of the body?

2) How do lymphocytes differ from phagocytes?3) What are antibodies and how do they help keep us from

harm?4) Which pathogen…

absorbs nutrients from living tissue?are prokaryotic?

5) Which illness is spread by mice?6) What is the vector of malaria?