IMMUNITY

ABBOTTS 2010

INFECTIONS AND IMMUNITY

TEXTBOOK PAGE 24

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INFECTIONS

Are caused by pathogenic Monera [viruses and bacteria] and Protista [Protozoans] and Fungi

An infection is the detrimental colonization of a host organism by a foreign species.

DEFINITION

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PATHOGENS

= disease causing micro-organisms

bacteria virus fungi, protozoa,

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IMMUNE RESPONSE BY PLANTS

Plant pathogens harm plant growth and reproduction Plants have an immune system to defend themselves

against infections

A plant recognizes the shape of the infecting pathogen and the infected cells are stimulated

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IMMUNE RESPONSE IN PLANTS

Produce salicylic acid a plant hormone or signal It is an asprin-like compound

Activate resistance genes which resist the pathogen – eg stop viral replication

Self destruct – form an area of dead cells to prevent the infection from spreading

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SYSTEMATIC ACQUIRED RESISTANCE

Salicylic acid moves from the infected site through the phloem to uninfected parts of the plant to activate the immune system to produce defensive compounds to make the entire plant resistant to the pathogen

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TO DO

TEXTBOOK PAGE 24

LEARNING ACTIVITY 15: IMMUNE RESPONSE BY PLANTS

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IMMUNE RESPONSE BY ANIMALS

TEXTBOOK PAGE 25

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FIRST LINES OF DEFENCE

skin prevents entry

tears antibacterial enzymes

saliva antibacterial enzymes

stomach acid low pH kills harmful microbes

mucus linings traps dirt and microbes

“good” gut bacteria out compete bad

Try to prevent the entry of germs

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PATHOGENS

= disease causing micro-organisms

bacteria virus fungi, protozoa,

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SECOND LINES OF DEFENCE

IF GERMS DO GET INTO THE BODY:

Primary response – tries to destroy the germs and prevent them from spreading

Secondary response – if germs do spread, the immune system is activated

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PRIMARY RESPONSE

Tries to destroy the germs and prevent them from spreading by:

Inflammation (if it is a local infection) Fever (raised body temperature)

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INFLAMMATION

Local infection Inflammation is a process

by which the bodies white blood cells protect us from infection and foreign substances such as bacteria and viruses

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SECONDARY RESPONSE/SPECIFIC RESPONSE

TEXTBOOK PAGE 25 If germs do start to spread Immune system becomes involved

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IMMUNITY

The body’s active response to an infection

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THE IMMUNE RESPONSE INVOLVES TWO MAIN MEASURES:

Destruction of the invading germs

Holding a memory of this response

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TWO GROUPS OF WHITE BLOOD CELLS INVOLVED IN THE IMMUNE RESPONSE

LYMPHOCYTES

B LYMPHOCYTES T LYMPHOCYTES

PHAGOCYTES

They are part of a huge army in ourbodiesThere are about one trillion B lymphocytesAnd one trillion T lymphocytesThey are found in the tonsils, lymph glands, spleen and blood

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ANTIGENS

all cells have surface markers called antigens.

body can recognise these as self or non-self (foreign)

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B LYMPHOCYTES

Also called antibody cells

If a germ gets into the body, it is detected by these cells

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HOW B LYMPHOCYTES DESTROY GERMS

Germs have molecules called antigens on their surface

The antigen tells the B lymphocyte that the germ is ‘non-human’ and dangerous

There are countless types of B lymphocytes

Each is able to recognize its own specific antigen

The B lymphocyte replicates rapidly producing lots of identical cells (clones)

These newly formed B lymphocytes produce proteins called antibodies into the blood plasma

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The antibodies combine with the antigens on the surface of the germ

DIAGRAM PAGE 25 – BINDING OF ANTIBODIES AND ANTIGENS

This will destroy or neutralise the germ

Some of the B lymphocytes stay in the lymph glands as memory cells

If they encounter the antigen again, they mount a response very quickly and kill the germ before it can breed

This is the basis of immunity

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HOW ANTIBODIES DESTROY GERMS

DIAGRAM: TEXTBOOK PAGE 25

METHODS OF GERM

DESTRUCTION BY ANTIBODIES

Antibodies could: Cause bacterial cells to burst Label germs for phagocytosis Cause germs to clump together

[clumps are easier to ingest by phagocytosis]

Neutralize bacterial toxins

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T LYMPHOCYTES

There are different types of T lymphocytes Each cell has a unique role to play in the

immune response CD4 Cells [helper T cells] Killer T cells

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CD4 cells are a type of white blood cell (lymphocyte

 Killer T cells

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CD4 CELLS/ HELPER T CELLS

Begin the immune response to infections Without these cells the other cells will not do

anything Body’s ability to fight infections would be very

poor

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KILLER T CELLS/ CYTOTOXIC T CELLS

They attack and destroy:

Cancer cells Cells infected with viruses

and some parasites Transplanted organs

[unless immunosuppressive drugs are given to the patient]

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TO DO

TEXTBOOK PAGE 26

LEARNING ACTIVITY 17

T LYMPHOCYTES AND IMMUNE RESPONSE

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PHAGOCYTES(CELLS THAT EAT!)

DIAGRAM TEXTBOOK PAGE 26

Are large lymphocytes (white blood corpuscles)

Can change shape They engulf germs by

phagocytosis [and also dead cells and foreign particles]

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HOW DO PHAGOCYTES DESTROY GERMS

Move around the body looking for germs

Squeeze through gaps in capillary walls and reach any part of the body

When it comes into contact with a germ, it engulfs it and takes the germ into the cell

Germ is digested and killed Process called

phagocytosis

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Phagocytosis of E coli

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TO DO

TEXTBOOK PAGE 27

LEARNING ACTIVITY 18: DEALING WITH INFECTIONS

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THE END

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