Question

Mention the source and the role of the following in providing defence against infection in the human body : (I) Histamine (II) Interferons

Hint:

Interferons do not cure cells that are already infected; instead, they function proactively to shield neighboring uninfected cells from spreading infection.

Answer 1

Concept: Innate immunity employs specialized chemical molecules to signal danger and halt cellular invasion during an active infection. (I) Histamine:
• Source: Secreted primarily by specialized connective tissue cells called Mast cells and circulating white blood cells known as Basophils during tissue damage or allergic encounters.
• Role in Defence: Acts as a potent vasodilator. It increases the diameter and permeability of local blood capillaries, allowing blood plasma and defensive phagocytic cells (like neutrophils and macrophages) to quickly leak out into surrounding tissues to fight off invading pathogens. This process triggers a localized inflammatory response. (II) Interferons:
• Source: Secreted explicitly by host cells that have already been invaded and infected by a virus.
• Role in Defence: These are cytokine barriers. Once released by a dying, infected cell, interferons travel to adjacent, healthy uninfected cells. They bind to specific surface receptors, triggering the synthesis of antiviral proteins (AVPs) that block viral replication, effectively shielding uninfected cells from the virus.