Defence mechanisms

Question 1

2 defence mechanisms of the body

Answer 1

-specific
-non specific

Question 2

What’s a specific response and give examples

Answer 2

response is slower and specific to each pathogen
-e.g. cell mediated response (T lymphocytes)
-humoral response (B lymphocytes)

Question 3

Whats a non specific response and give example

Answer 3

response is immediate and same for all pathogens
-eg physical barrier (like skin)
-phagocytosis

Question 4

How do body recognise own cells

Answer 4

-lymphocytes distinguish own bod cells as non-self/self
-have specific proteins (antigens) on its cell surface membrane , much variety with highly specific tertiary structure
-can identify (non-self): pathogens, non-self material, toxin (from bacteria) , abnormal body cells

Question 5

Why can defence mechanism cause issues for transplant patients

Answer 5

-immune system recognises these as non-self cells even though same species
-so attempt to destroy transplant
-minimise rejection: donor tissue matched closely e.g. relative + administered immunosuppressant drugs to reduce level of immune response that still occurs

Question 6

What happens when an infection occurs

Answer 6

-lymphocytes have proteins on surface that are complementary to one of the proteins on pathogen
-presence of infection, one type already present that have complementary proteins to those of pathogen is stimulated to divide
-this builds up its numbers so it ca effectively destroy it (clonal selection)

Question 7

How lymphocytes recognise cells belonging to body in fetus

Answer 7

-in fetus, lymphocytes constantly colliding with other cells
-infection in fetus is rare because it is protected from outside world (mother + placenta)
-so lymphocytes collide almost exclusively with body’s own material (self)
-some lymphocytes will have receptors that exactly fit those of body’s own cells so these lymphocytes either die/suppressed
-remaining lymphocytes are those that might fit foreign material and therefore only respond to foreign material

Question 8

How lymphocytes recognise cells belonging to body in adults

Answer 8

-lymphocytes produced by bone marrow initially only encounter self antigens
-any lymphocytes that shows immune response to those self antigens undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes
-No clones of these anti self lymphocytes will appear in blood, leaving only those that will respond to non self antigens

Question 9

Where do T lymphocytes mature and associated with

Answer 9

-Thymus
-cell-mediated immunity

Question 10

Where do B lymphocytes mature and associated with

Answer 10

-Bone marrow
-humoral immunity