Question

(i) What is immunity?
(ii) Write the difference between active immunity and passive immunity.
(iii) Explain passive immunization.
(iv) Draw the labeled diagram of the stages of life cycle of Plasmodium in mosquito host.

Answer 1

(i) Immunity is the state which provides the ability to protect the body against any infection. This is the physiological state in which the body is healthy enough to fight against any disease condition.

(ii)

Active immunity	Passive immunity
It is produced due to contact with pathogen or antigen.	It is produced due to antibodies obtained directly.
It lasts for a long time.	It lasts for few days.
Antibodies are produced by the body against the antigen.	Antibodies are obtained from other sources.
Immunity is not immediate. There is a time lapse for the development.	Immunity develops immediately.
There are no or little side effects.	The introduction of antisera can cause serum sickness.
The person is exposed to the agent.	The person is not exposed to the agent but is given the antibodies.

(iii) Passive immunity is the transfer of active humoral immunity in the form of ready-made antibodies, from one individual to another. Passive immunity can occur naturally when maternal antibodies are transferred to the fetus through the placenta or can be induced artificially when high levels of human antibodies specific for a pathogen or toxin are transferred to non-immune individuals.

(iv) Plasmodium completes its life cycle in two phases, asexual phase in human blood and sexual phase in mosquitoes. The life cycle of the Plasmodium in the mosquito is described in the given figure.