Immunity

Antibodies• Lymphocytes in WBC produce chemicals called antibodies• Each lymphocytes produces a specific type of antibody.• Antibodies – chemicals secreted by lymphocytes, which attach to

antigens and help destroy them.• Antigen – chemicals on the surface of pathogens, which are

recognised as foreign by the body.

• The job of the antibody is to kill the pathogen• How?• Coats the surface of the pathogen – preventing entrance• Alert phagocytes, to come and destroy pathogens

Question?• Do you think it is a good use of the bodies resources to be constantly

producing and secreting antibodies?

• No.

• The lymphocytes wait for a signal that a pathogen is present which can be destroyed by the lymphocytes particular antibodies

What happens?Pathogen enters the body |Met by many different lymphocytes |A lymphocyte will recognise the pathogen as something its antibodies can destroy |Rapidly divides (mitosis) to create clones of itself |These lymphocytes then secrete their antibodies, overwhelming the pathogen

What affects the time it takes to produce the antibodies?Firstly, the lymphocytes may take time to recognise the pathogen

Then it takes time to produce enough lymphocytes that can secrete enough antibodies

Meanwhile, the pathogen is reproducing

Extra defense• Memory cells – cells produced by lymphocytes that remain in the

body and are able to respond quickly to a pathogen

• Next time the same type of pathogen enters the body, memory cells react quickly• Destroying the pathogen before it has time to reproduce itself

(fig.10.13)

Question?• If a person is infected with a disease (first infection), why does it take

time for him/her to get better?

• Firstly, lymphocytes take time to recognise the specific pathogen.• Secondly, it takes time for the lymphocytes to clone themselves

enough to produce enough antibodies to kill the pathogen• Thirdly, the pathogen is reproducing itself during this time

Vaccination• Introduction into the body of dead or weakened pathogens, to make

the person immune to an infectious disease.

2 types of Immunity• Active immunity – long term defense - getting over the disease - vaccination• Passive immunity – short term defense - "antibodies acquired from another individual" - mother to baby through breast milk - injection of antibodies

• Active immunity can be very long lasting. = sometimes a whole lifetime = sometimes need "booster shots"

• Passive immunity is short term. = The body has not made memory cells = Antibodies eventually breakdown

Rabies bite case study• The woman could have been vaccinated against rabies before going to

India• What would have happened?• The woman could have been given an emergency injection of

antibodies.• What would have happened?

Why is vaccination a good idea?• Smallpox completely eradicated• Polio is now rare• Controls infectious diseases

Auto-immune diseases• "a disease caused by a person's own immune system attacking parts

of their body"

• Lymphocytes react to a person's own cells as if they were pathogens• Eg. Type 1 Diabetes

Type 1 Diabetes• Beta cells in the pancreas produce insulin (controls glucose levels in

blood)• In people with type 1 diabetes, the lymphocytes attack these beta

cells• Loss of beta cells = insulin is no longer produced (glucose levels not

controlled)• People with type 1 diabetes usually take insulin injections and must

watch their diets.