Question:
Study the following statements regarding immune system and identify the correct statements.
A) Humoral immunity helps in apoptosis.
B) Destruction of microbes by natural killer cells is called first line of defence.
C) The mature lymphocytes are transformed into functional lymphocytes in appendix.
D) The attack of HIV on certain tissues is referred as tissue tropism.
Study the following statements regarding immune system and identify the correct statements.
A) Humoral immunity helps in apoptosis.
B) Destruction of microbes by natural killer cells is called first line of defence.
C) The mature lymphocytes are transformed into functional lymphocytes in appendix.
D) The attack of HIV on certain tissues is referred as tissue tropism.
A) Humoral immunity helps in apoptosis.
B) Destruction of microbes by natural killer cells is called first line of defence.
C) The mature lymphocytes are transformed into functional lymphocytes in appendix.
D) The attack of HIV on certain tissues is referred as tissue tropism.
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Remember: Primary lymphoid organs (bone marrow, thymus) are sites of lymphocyte production and maturation.
Secondary lymphoid organs (spleen, lymph nodes, tonsils, Peyer's patches, appendix) are sites where mature lymphocytes become functional effector cells.
Secondary lymphoid organs (spleen, lymph nodes, tonsils, Peyer's patches, appendix) are sites where mature lymphocytes become functional effector cells.
Updated On: Jul 22, 2026
- C & D
- A & C
- B & D
- A & B
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Question:
We need to analyze four statements about the mammalian immune system to find the correct combination.
Step 2: Key Concept and Approach:
We will evaluate each statement's biological accuracy:
- Humoral immunity involves antibodies, while apoptosis of infected cells is mediated by cell-mediated cytotoxicity.
- Natural killer (NK) cells are part of cellular innate immunity, acting as the second line of defense.
- Secondary lymphoid organs like the appendix are sites where mature lymphocytes interact with antigens and differentiate.
- Viruses targeting specific cell types containing matching receptors exhibit tissue tropism.
Step 3: Detailed Explanation:
• Statement A: Humoral immunity is mediated by macromolecules (antibodies) secreted by B-cells, primarily neutralizing extracellular pathogens.
Apoptosis induction in target cells is a feature of cell-mediated immunity (via Cytotoxic T-lymphocytes).
Thus, Statement A is incorrect.
• Statement B: The first line of defense consists of physical and chemical barriers (e.g., skin, stomach acid).
NK cells represent cellular barriers, which form the second line of defense.
Thus, Statement B is incorrect.
• Statement C: The appendix is a secondary lymphoid organ.
In secondary lymphoid organs, mature (but naive) lymphocytes are exposed to foreign antigens, undergo clonal selection, and transform into functional effector cells.
Thus, Statement C is correct.
• Statement D: HIV specifically infects CD4+ T-helper cells and macrophages.
This preference for specific host tissues or cells is called tissue tropism.
Thus, Statement D is correct.
• Therefore, statements C and D are correct.
Step 4: Final Answer:
The correct statements are C and D, matching Option (A).
We need to analyze four statements about the mammalian immune system to find the correct combination.
Step 2: Key Concept and Approach:
We will evaluate each statement's biological accuracy:
- Humoral immunity involves antibodies, while apoptosis of infected cells is mediated by cell-mediated cytotoxicity.
- Natural killer (NK) cells are part of cellular innate immunity, acting as the second line of defense.
- Secondary lymphoid organs like the appendix are sites where mature lymphocytes interact with antigens and differentiate.
- Viruses targeting specific cell types containing matching receptors exhibit tissue tropism.
Step 3: Detailed Explanation:
• Statement A: Humoral immunity is mediated by macromolecules (antibodies) secreted by B-cells, primarily neutralizing extracellular pathogens.
Apoptosis induction in target cells is a feature of cell-mediated immunity (via Cytotoxic T-lymphocytes).
Thus, Statement A is incorrect.
• Statement B: The first line of defense consists of physical and chemical barriers (e.g., skin, stomach acid).
NK cells represent cellular barriers, which form the second line of defense.
Thus, Statement B is incorrect.
• Statement C: The appendix is a secondary lymphoid organ.
In secondary lymphoid organs, mature (but naive) lymphocytes are exposed to foreign antigens, undergo clonal selection, and transform into functional effector cells.
Thus, Statement C is correct.
• Statement D: HIV specifically infects CD4+ T-helper cells and macrophages.
This preference for specific host tissues or cells is called tissue tropism.
Thus, Statement D is correct.
• Therefore, statements C and D are correct.
Step 4: Final Answer:
The correct statements are C and D, matching Option (A).
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