DMPQ: What is immunity? Explain the types of immunity?

Immunity is the ability of the body to fight against infectious agents. The immunity can be classified as innate immunity and acquired immunity.

1. Innate immunityis a non-specific type of defense mechanism.  It has four types:
2. i) Physical barrier: Example, skin covering of the body, secretion of mucous in the respiratory tract

ii)Physiological barrier: Example, acid in the stomach, tears from the eyes

iii) Cellular barrier: Example, monocytes and lymphocytes in blood

1. Cytokine barrier: Example, interferon
2. Acquired immunity:it is a specific type of defence mechanism. It shows two types of responses: primary response and secondary response. It involves two types of lymphocytes – 

• B lymphocytes: Show humoral immune response (HI)
• T lymphocytes: Show cell mediated immunity (CMI)