What are the four types of barriers in innate immunity?

The correct answer is Option (1) → Physical, physiological, cellular, cytokine

Innate immunity is the non-specific defence present from birth. It works by putting barriers in the way of foreign agents.

Option (1) Physical, physiological, cellular, cytokine — Correct. These are the four barriers of innate immunity. Physical barriers (skin, mucus) stop entry; physiological barriers (stomach acid, saliva, tears) stop microbial growth; cellular barriers are white blood cells such as neutrophils, monocytes, natural killer cells and macrophages that engulf microbes; cytokine barriers are interferons, which protect non-infected cells from viruses.

Option (2) Antibody, antigen, lymphocyte, leukocyte — Incorrect. Antibodies, antigens and lymphocytes belong to acquired immunity. An antigen is the foreign substance itself, not a barrier against it.

Option (3) B-lymphocyte, T-lymphocyte, macrophage, neutrophil — Incorrect. This is a list of cell types. B- and T-lymphocytes carry out acquired immunity; only neutrophils and macrophages belong to innate immunity, and together they make up just one barrier, the cellular barrier.

Option (4) Primary, secondary, humoral, cell-mediated — Incorrect. These words describe acquired immunity: primary and secondary responses, humoral (antibody-mediated) immunity and cell-mediated immunity. They are not barriers of innate immunity.

NCERT Extract:
Innate Immunity – “Innate immunity is non-specific type of defence, that is present at the time of birth. This is accomplished by providing different types of barriers to the entry of the foreign agents into our body. Innate immunity consist of four types of barriers. These are — (i) Physical barriers : Skin on our body is the main barrier which prevents entry of the micro-organisms. … (ii) Physiological barriers : Acid in the stomach, saliva in the mouth, tears from eyes–all prevent microbial growth. (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.”