Immunity & Cancer
Read the following passage carefully and answer the given questions.
If the pathogens succeed in gaining entry to our body, specific antibodies and cells serve to kill these pathogens. The B-lymphocytes produce an army of proteins in response to pathogens into our blood to fight with them. The T-cells themselves do not secrete antibodies but help B cells to produce them. The principle of immunisation or vaccination is based on the property of ‘memory’ of the immune system. In vaccination, a preparation of antigenic proteins of pathogen or inactivated/weakened pathogen (vaccine) are introduced into the body. The antibodies produced in the body against these antigens would neutralise the pathogenic agents during actual infection. The exaggerated response of the immune system to certain antigens present in the environment is called allergy. The human immune system consists of lymphoid organs, tissues, cells and soluble molecules like antibodies. Cancer causing viruses called oncogenic viruses have genes called viral oncogenes. Furthermore, several genes called cellular oncogenes (c-onc) or proto oncogenes have been identified in normal cells which, when activated under certain conditions, could lead to oncogenic transformation of the cells.
Which one of the following is an example of primary lymphoid organ?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Thymus
Primary lymphoid organs are where immature lymphocytes develop into lymphocytes that can recognise antigens. Secondary lymphoid organs are where these lymphocytes meet antigens and multiply.
(1) Mucosa-associated lymphoid tissue — Incorrect. It lies in the lining of the respiratory, digestive and urogenital tracts. It is a secondary lymphoid tissue, though it makes up about half of all lymphoid tissue in the body.
(2) Peyer’s patches — Incorrect. These are secondary lymphoid organs in the small intestine.
(3) Spleen — Incorrect. The spleen is a secondary lymphoid organ. It filters the blood and stores red blood cells.
(4) Thymus — Correct. The thymus lies near the heart, beneath the breastbone. T-lymphocytes develop and mature here. Along with the bone marrow, it is a primary lymphoid organ.
Note 1: This passage is taken from NCERT as it is. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
Note 2: A similar question was also asked in CUET (UG) 2023 on 15-06-2023 (Slot 1), and in CUET (UG) 2022 on 23-08-2022 (Slot 3).
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.”