Ch 3 – The Immune System

3.2 Factors Affecting the Immune System

Immunity• Recall: if our bodies contain the

antibodies for specific antigens, we have what is called “immunity”.

• We develop immunity when we get sick and our body makes antibodies to fight an antigen.

• We can also obtain immunity by receiving a vaccine (vaccination).

Vaccines• A vaccine is a

special version of an antigen.

• It is a weakened form of the disease

• Administered by needle usually (liquid form)

How do vaccines work?• A small amount of weakened disease

enters the body• Your immune system creates antibodies to

fight the disease• You don’t become ill because there is such

a small amount of weakened disease• But some antibodies remain…

– They can be reactivated if the antigen enters your body in the future

More about vaccines• Vaccines can be a

one-shot deal or you may get another vaccination every few years.

• For example, we get tetanus shots every 10 years to bolster antibody production.

• Some vaccines you receive as a baby

Are vaccines risky?• No, not generally• Most vaccines are

accompanied by mild side effects that don’t last long

• Sometimes a severe allergic reaction can occur but this is rare.

Extreme reaction to smallpox vaccine

Disorders of the Immune System

• Some people have an unusually high sensitivity to a certain substance. – When the substance

enters their body, the immune system recognizes it as an invader and the system over-reacts!

– This sensitivity is called an allergy

Allergies• There are many things that can

cause allergies. – Food (milk, gluten, peanuts,

strawberries…)– Pollen, dust– Cats, beestings

Any substance that causes an allergic reaction is called an “allergen”.

Did You Know?• Dust allergies may

actually be due to the feces of dust mites that live in house dust!

• Dust mites eat dead skin flakes and make their home in your bed, carpet and old clothing!

Allergy Symptoms• Common symptoms of an allergy

– Runny nose– Watery eyes• Why does this happen?

• When your body needs to fight an invader (an allergen) it releases a chemical called histamine

• Runny noses and watering eyes are side-effects of histamine

• We use drugs called anti-histamines to reduce these symptoms

Severe Allergic Reactions• Some people have more severe allergies

– Ex: peanuts, bee-stings• If they come in contact with these

allergens they can have a severe reaction called anaphylactic shock

• Results in swelling, difficulty breathing, can be fatal

• People often carry adrenaline-shots (EpiPen) to reduce the effects.

Disorders of the Immune System

• AIDS – Acquired Immunodeficiency Syndrome

• Infection of the immune system that can lead to death

• Caused by a virus called human immunodeficiency virus (HIV)

• HIV is a fierce pathogen that attacks the immune system and destroys it

What does HIV do to the body?• HIV infects helper T cells

– Since helper T cells activate B cells, your body can no longer activate B cells or killer T cells

– The immune system has no way to fight the pathogen

– In other words, the immune system shuts down

– Other antigens or pathogens can enter and your body has no way to fight against them

How is HIV transmitted?• HIV can be

transmitted through – Blood– Semen

• HIV cannot be transmitted through– Direct contact

• Shaking hands– Saliva

• Sharing drinks, kissing

Cure for AIDS? • There is currently no

known cure for AIDS• HIV keeps changing its

structure slightly • There are also several

forms of the virus• A person infected with

HIV live 4-10 years• AIDS currently affects

more than 40 million people

Keeping Your Immune System Healthy

• What can you do?– Eat healthy foods– Exercise– Wash your hands– Keep yourself and

your home clean– Avoid drugs/ tobacco– Get enough sleep– Get vaccinations– Be cautious (don’t

share drinks, etc..)