Immunity

ImmunityObjectives

• Explain how the immune system works.

• Explain the difference between passive and active immunity.

• Discuss the dangers of different diseases around the world.

• Explain how and why new drugs are tested.

– Starter Explain in as much detail as possible why a person doesn’t usually get chicken pox twice.

Key Words

• antibiotics • antibodies • antigens • antivirals • immunisation • immunity • memory cells

• placebos • toxins • vaccine

Pathogens

• Any organism that causes disease in another.Most pathogens have to get inside our body to spread infection. Once they are inside, the body provides ideal living conditions - plenty of food, water and warmth. Standing in their way is our body's immune system - a collective name for the body's co-ordinated response to the invading pathogens.

Diseases. Bacteria

Fungi

Virus

Bacteria

E.Coli (scanning electromicrograph)

Contact lens bacteria!

Dental plaque bacteria

Psoriasis – caused by bacteria

Cholera

Tetanus

Gangrene – caused by bacteria

Influenza - flu

Measles – caused by a virus.

Chickenpox!

Bread mold spores

Athletes Foot – caused by fungi

Thrush – caused by fungi

Infected Nails – caused by fungi

Things you can do:• Don't smoke • Protect yourself in the sun • Eat a healthy diet - plenty of fruit and veg • Cut down on red meat • Don't drink too much alcohol • Keep your body at a healthy weight - not too skinny and

not too fat! • Exercise • Be aware of changes on your body • Make sure you check yourself for unusual lumps • Get any suspicious lump or mark checked out by a doctor.

Infected.

• The symptoms of an infectious disease are caused by cell damage or by toxins produced by the pathogens that have got into the body.

• The invaders can produce chemicals, toxins or enzymes, which the immune system considers as not the body's own. It is not the microorganisms themselves but the protein markers on the cell surface or the chemicals they produce that are recognised as foreign substances. These markers which trigger the immune response are called antigens.

• Each pathogen has its own antigens, specific antibodies are needed to destroy pathogens with different antigens.

• Antibodies lock on to antigens causing the death of the pathogens.

Human blood sample

Immunisation

1) harmless pathogen given - this carries antigens, antigens trigger immune response.

2) by producing antibodies, immunity remains.

Specificity of antibodies

How white blood cells work

Active immune system

• Active immunisation is achieved by stimulating the body to produce its own antibodies.

• Vaccinating people against particular diseases is an example of active immunity

Vaccination• Vaccinations are an

effective way of stimulating the body’s own defences so that we need not suffer the infectious diseases, such as measles, mumps and whooping cough, that used to be a common feature of childhood.

Immunisation

Harmless form of disease organism given.

Harmless form still carries antigens – trigger immune response – antibodies made

Immunity remains

Passive immune system• When you are given the anti-biotics – you don’t

make them yourselves.

• Antibodies made by another organism can be injected into a person. This is used when there isn't sufficient time for the person to produce their own antibodies, eg in the case of a snakebite. However, the injected antibodies are seen as foreign proteins by the body's immune system, so they are treated as antigens and destroyed fairly quickly. Passive immunisation is therefore only a short-term solution.

Testing new drugs

• Animals

• Human tissue

• Computer models

• What objections could there be to these forms of testing.

• The use of blind and double blind trials in testing new drugs against placebos.

The human immune system defends the body from diseases caused by micro-organisms. These

pathogens need to be recognised as being harmful to the body

1. a What is a pathogen?

b Give two examples in your answer.

2. What are antigens?

3. What are the cells in the human body that are involved in the immune system?

4. a What are antibodies?

b Why are they specific for just one type of antigen?

5. Describe how antibodies destroy pathogens?

1. What is contained in a vaccine?

2. Explain why live pathogens are not used in a vaccination.

3. How does the body’s immune system respond to the vaccine?

4. Explain the difference between the primary response and the memory response.

5. a Explain why “memory white blood cells” (lymphocytes) are important.

b How long do they last in the body?

6. Why does a particular vaccine only give immunity against one disease?

ILL HEALTH / DISEASE

poor diet, e.g. scurvy, rickets

inherited from parentse.g. cystic fibrosis sickle cell anaemia

cells divide / growabnormally / mutation - cancer

Effect of lifestylee.g. heart / lung disease & smoking,liver damage & alcohol

Parts of the body are damaged / worn oute.g. heart disease, diabetes.

Infection bye.g. bacteria e.g. tetanus; viruses e.g. measles, AIDS;fungi e.g. athlete’s foot.

WHY DO WE GET ILL ?