immunity

Question 1

define immunity

Answer 1

permanent or temporary resistance to disease
can be described as being active or passive
can be acquired naturally or artificially

Question 2

what is responsible for defending the body against disease

Answer 2

white blood cells

Question 3

define herd immunity

Answer 3

occurs when a high percentage of the community is immune to a disease
through vaccination and/or prior illness

Question 4

explain active immunity

Answer 4

white blood cells come into contact with an antigen(specific proteins on surface of a pathogen) resulting in an immune response
immune response involves production of antibodies by lymphocytes
antibodies produced are specific to antigens encountered
antibody production is slow at first so that pathogen is able to multiply and affect cells, causing symptoms
eventually large numbers of antibodies allows for destruction of pathogens and symptoms pass
memory cells are produced which remain in blood long after infection has disappeared
this allows a much faster production of antibodies if ever the person is re-infected with the same pathogen carrying same antigen

Question 5

how long does active immunity last

Answer 5

short time to a lifetime

Question 6

define antibodies

Answer 6

antibodies are proteins produced by lymphocytes in response to antigens
can be categorised according to how they deal with pathogens

Question 7

define opsonins

Answer 7

adhere to outer surface of bacteria and so make it easier for phagocytes to ingest them

Question 8

agglutinins

Answer 8

cause bacteria to stick together in clumps, preventing them from invading tissues

Question 9

lysins

Answer 9

dissolve outer coats of pathogens, dissolving them

Question 10

anti-toxins

Answer 10

neutralise poisonous toxins produced by pathogens

Question 11

explain how natural active immunity works

Answer 11

person becomes infected with a pathogen (bacteria) via natural means such as through droplets from an infected person’s cough or sneeze
lymphocytes in blood come into contact with pathogen and produce antibodies specific to antigen on pathogen
antibodies get rid of pathogens
first infection-person has symptoms
second infection - persons memory cells cause lymphocytes to produce antibodies faster so they are able to destroy pathogens before symptoms appear
person is said to be immune
some immunity can last a lifetime (measles) or for a shorter period of time (influenza)

Question 12

describe artificial active immunity

Answer 12

person is vaccinated
vaccine contains dead or weakened form of a specific pathogen preventing pathogen from causing any harm to person
dead/weak pathogen contains antigens on surface which bring about an immune response
memory cells are produced
immunity may last for a lifetime (yellow fever) or for a shorter period of time (tetanus 7-10 years)

Question 13

what is ring vaccination

Answer 13

controls an outbreak by vaccinating and monitoring a ring/group of people around each infected individual or a group of persons who have a higher risk of becoming infected
used to control smallpox until last naturally occurring case in 1977

Question 14

define passive immunity

Answer 14

body does not produce its own antibodies but rather ready made antibodies are passed on person
antibodies will fight pathogens in their usual manner
antibodies only life for short period of time therefore passive immunity is short lived
no memory cells produced so there is no immunity in event of future infections
passive immunity can be acquired artificially or naturally

Question 15

explain natural passive immunity

Answer 15

antibodies are passed on from a mother to her foetus via placenta or form a mother to her baby through breastfeeding
antibodies made by mother in response to any infections the mother had
foetus/baby will be immune to same diseases that mother is
since foetus/baby did not actively make antibodies there are no memory cells and immunity only lasts as long as antibodies remain present in blood
immediate but short-lived

Question 16

explain artificial passive immunity

Answer 16

person is injected with antibodies for a particular pathogen
to differentiate between this type of injection and one discussed earlier usually called antiserum
this is usually given after a person has been exposed to a possible infection
person who has stepped on a rust nail can receive tetanus antiserum instead of a tetanus vaccine
provides immediate immunity but is short lived