Which of the following is an example of a cytokine barrier?

The correct answer is Option (1) → Interferons

Innate immunity is the non-specific defence present at birth. It works through four kinds of barriers: physical (skin, mucus), physiological (stomach acid, saliva, tears), cellular (phagocytic leukocytes) and cytokine barriers. The cytokine barrier is made of proteins that cells secrete to protect other cells.

Option (1) Interferons — Correct. Interferons are proteins secreted by virus-infected cells. They protect the cells that are not yet infected from further viral infection, so they form the cytokine barrier.

Option (2) T-lymphocytes — Incorrect. T-lymphocytes are cells of acquired immunity. They bring about the cell-mediated immune response and are not secreted proteins.

Option (3) B-lymphocytes — Incorrect. B-lymphocytes are also cells of acquired immunity. They produce antibodies in the humoral immune response.

Option (4) T_H cells — Incorrect. T_H cells (helper T-lymphocytes) are T-lymphocytes that help other immune cells respond. They are cells of acquired immunity and the main target of HIV, not a cytokine barrier.

NCERT Extract:
Innate Immunity – “… Innate immunity consist of four types of barriers. These are — … (iii) Cellular barriers : Certain types of leukocytes (WBC) of our body like polymorpho-nuclear leukocytes (PMNL-neutrophils) and monocytes and natural killer (type of lymphocytes) in the blood as well as macrophages in tissues can phagocytose and destroy microbes. (iv) Cytokine barriers : Virus-infected cells secrete proteins called interferons which protect non-infected cells from further viral infection.”