Define immunity and name two different types of immunity.

Explanation

It is the overall ability of the host to fight the disease-causing organisms conferred by the immune system.
(i) Innate immunity and
(ii) Acquired immunity.

Detailed Answer:
(a) Immunity
It is the ability of the immune system of the body to fight against the dis ease-causing organisms.
It is of two types namely Innate inmunity and Acquired immunity.
(i) Innate Immunity
It is the non-specific defense present at the time of birth.
It provides barriers to the entry of foreign agents into our body.
(ii) Acquired Immunity
It is a pathogen specific immunity.
It is not present since birth but develops during the life time of an individual.
It is characterized by memory i.e. during first encounter of a pathogen, our body produces primary.
response in low intensity. Second encounter with the same pathogen produces a secondary (anamnestic). response in high intensity.
The primary and secondary immune responses are carried out with B-lymphocytes and T-lymphocytes.
B-lymphocytes (B-cells): Produce antibodies.
T-lymphocytes : Help B-cells to produce antibodies.