Immunity

Question 1

immunity

Answer 1

Immunity is the temporary or permanent resistance to a disease.

Question 2

natural immunity

Answer 2

results from a person having been exposed to a pathogenic disease caused by a virus or bacterium.

Question 3

antigens

Answer 3

foreign substances

chemicals, mainly proteins, found in the walls or coats of pathogens, or the toxins pathogens produce

Question 4

lympocytes

Answer 4

Lymphocytes bring about this immunity by producing proteins calledantibodiesin response to the presence

Question 5

antigens are

Answer 5

specific to the type of pathogen andare foreignto all other organisms.

Question 6

lympocytes do what

Answer 6

Whena pathogen enters the body, lymphocytes make specific antibodies in response to the pathogen’s specific antigen.

Question 7

antibodies can

Answer 7

• Cause the pathogens to clump together so that thephagocytes can engulf them, or* Cause the pathogens to disintegrate, or
• Neutralise the toxins produced by the pathogens; antibodies that do this are called antitoxins.

Question 8

continued

Answer 8

Production of antibodies takes time and the pathogen produces symptoms of disease before beingdestroyed or having its toxins neutralised. Once the person recovers, the antibodies gradually disappear from the blood and some lymphocytes develop intolymphocyte memory cells that remember the specific antigen.

Question 9

continued why artificial immunity works

Answer 9

When the pathogen enters the body again, these memory lymphocytes recognise the antigen,multiply and quickly produce large quantities of the specific antibody. The pathogen is destroyed or itstoxins neutralised before symptoms of the disease develop. The person has becomeimmune to thedisease. Immunity may last a short time, e.g. against the common cold, to a lifetime, e.g. chicken pox is rarely caught twice.

Question 10

how a baby gains immunity

Answer 10

A baby gains important immunity by receiving antibodies that pass across the placenta before birthor frombreast milk during breast feeding. Sincethe baby’s lymphocytes have not been involved inproducing the antibodies and the antibodies gradually disappear from the blood, immunity lasts only a short time.

Question 11

artifical immunity

Answer 11

acquired by vaccination and is used to control the spread of communicable diseases, i.e. diseases that pass from person to person

Question 12

vaccine may contain

Answer 12

• Live pathogens that have been weakened (attenuated), e.g. measles, mumps and rubella vaccines.
• Pathogens that have been killed, e.g. cholera, influenza and polio vaccines.
• Toxins from the pathogen that have beenmade harmless, e.g. diphtheria and tetanus vaccines.
• Fragments of the pathogen, e.g. influenza vaccine.
• The specific antigens (proteins) from the coat of the pathogen produced by genetic engineering, e.g. hepatitis B vaccine

Question 13

WHAT VACCINES DO

Answer 13

Vaccines do not cause the disease, but lymphocytes still makeantibodies in response to the specific antigens that are present in the vaccine. Lymphocyte memory cells are also produced so that an immune response is set up whenever the pathogen enters the body. Artificial immunity may last a short time, e.g. against cholera, to a lifetime, e.g. against tuberculosis.

Question 14

reasons why the vaccines should or should be taken

Answer 14

education, missing of school
reduces spread of the disease

do not want to relase pathogens inside child’s body
may be allergic to the composition of the vaccine
does not know what the vaccine contains
beliefs