Read the passage carefully and answer the questions given below.
Our immune system plays the major role in preventing diseases when we are exposed to disease-causing agents. Immunity is of two types: (i) Innate immunity and (ii) Acquired immunity. The human immune system consists of lymphoid organs, tissues, cells and soluble molecules like antibodies. The immune system also plays an important role in allergic reactions, auto-immune diseases and organ transplantation. The primary lymphoid organs are bone marrow and thymus. The secondary lymphoid organs are spleen, lymph nodes, tonsils, Peyer's patches of small intestine and appendix. There is lymphoid tissue also located within the lining of the major tracts (respiratory, digestive and urogenital tracts) called mucosa associated lymphoid tissue (MALT). It is important to note that HIV/AIDS is not spread by mere touch or physical contact it spreads only through body fluids. AIDS has no cure, prevention is the best option. Adolescence is accompanied by several biological and behavioural changes and surveys and statistics show that use of drugs and alcohol has been on the rise especially among the youth. Factors associated with drug and alcohol abuse among adolescents are a child's natural curiosity, stress, the perception among youth that it is 'cool' or progressive to smoke, media exposure and an unstable or unsupportive family structures and peer pressure. It is best to identify the situations that may push an adolescent towards use of drugs or alcohol, and to take remedial measures well in time.
Which one of the following structures is not an example of a cellular barrier in innate immunity?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Protein interferon
Innate immunity is the defence present from birth. It works through four kinds of barriers: physical (skin, mucus), physiological (stomach acid, saliva, tears), cellular (white blood cells that eat microbes) and cytokine (interferons).
Option (1) Protein interferon — Not a cellular barrier. Interferons are proteins, not cells. Virus-infected cells release them to protect the cells not yet infected, so they form the cytokine barrier.
Option (2) PMNL neutrophils — A cellular barrier. PMNL stands for polymorpho-nuclear leukocytes. These neutrophils are white blood cells in the blood that engulf and destroy microbes (phagocytosis).
Option (3) Lymphocytes — A cellular barrier. The natural killer cells, a type of lymphocyte, are part of the cellular barrier of innate immunity.
Option (4) Macrophages — A cellular barrier. Macrophages in the tissues phagocytose microbes, like the neutrophils in the blood.
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:
Innate Immunity – …
