Question

The graph below shows the Antibody concentration in young calves. Study the graph and answer the questions that follow:

1. What do you think the difference is between passive and active immunity in this case?    (1)
2. What kind of immunity will be observed when a vaccine is administered to the calf and why?    (2)
3. What kind of trend does passive immunity show and why?    (1)
   OR
4. Why does active immunity start after 14 days, as per the above graph?

Answer 1

1. Passive immunity is provided immediately after birth through colostrum, containing ready-made antibodies from the mother. It provides instant protection but is short-lived.
   Active immunity develops later when the calf’s own immune system starts producing antibodies in response to antigens. It is slow to develop but provides long-lasting protection.
2. When a vaccine is administered, the calf develops active immunity.
   This is because vaccines contain weakened or dead pathogens that stimulate the calf’s immune system to recognize and produce specific antibodies. The immunity takes time to build but becomes long-lasting and specific to the pathogen.

3. Trend: Passive immunity shows a sharp increase immediately after birth and then a gradual decline over time.
   Reason: This is because the calf absorbs high levels of maternal antibodies from colostrum shortly after birth, but these antibodies are not replenished, so their concentration declines naturally over time as they are used or degraded.
   OR

4. Active immunity is slow because the calf’s immune system takes time to develop and respond to pathogens.