Read the following passage carefully and answer the given questions.
Plasmodium, a tiny protozoan is responsible for the disease malaria. Different species of Plasmodium (P. vivax, P. malaria and P. falciparum) are responsible for different types of malaria. Of these, malignant malaria caused by Plasmodium falciparum is the most serious one and can even be fatal. 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. Allergy is due to the release of chemicals like histamine and serotonin from the mast cells. The use of drugs like anti-histamine, adrenalin and steroids quickly reduce the symptoms of allergy. Drugs like barbiturates, amphetamines, benzodiazepines, and other similar drugs, that are normally used as medicines to help patients cope with mental illnesses like depression and insomnia, are often abused.
Which one of the following is not the example of cellular barrier?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Peyer’s patches
Cellular barriers are one of the four barriers of innate immunity. They are white blood cells that engulf and destroy microbes (phagocytosis) as soon as these enter the body.
Option (1) Leukocytes — A cellular barrier. Leukocytes are the white blood cells. Certain leukocytes, such as the polymorpho-nuclear leukocytes (PMNL-neutrophils), phagocytose microbes in the blood.
Option (2) Monocytes — A cellular barrier. Monocytes are leukocytes of the blood. They also take in and destroy microbes, and the passage lists them among the cellular barriers.
Option (3) Peyer’s patches — Not a cellular barrier. Peyer’s patches are small masses of lymphoid tissue in the wall of the small intestine. They are a secondary lymphoid organ, a place where mature lymphocytes meet antigens. They belong to the acquired immune system, not to the cells that act as an innate barrier.
Option (4) Macrophages — A cellular barrier. Macrophages are large phagocytic cells that stay in the tissues. They engulf and destroy microbes that cross the skin and the other barriers.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Immune System in the Body – “… Lymphoid organs: These are the organs where origin and/or maturation and proliferation of lymphocytes occur. The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate into antigen-sensitive lymphocytes. After maturation the lymphocytes migrate to secondary lymphoid organs like spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix. The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells.”