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

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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)