Use the correct option at the appropriate place.
The white blood cells ( ) within the immune system identify and destroy foreign bodies ( ) such as viruses.
Use the correct option at the appropriate place.
The white blood cells ( ) within the immune system identify and destroy foreign bodies ( ) such as viruses.
Options
Correct option: (D) Leucocytes/Antigens.
The white blood cells are called leucocytes, and the foreign bodies (like viruses) that they identify and destroy are called antigens — so the sentence reads: 'The white blood cells (Leucocytes) within the immune system identify and destroy foreign bodies (Antigens) such as viruses.'
Marking Scheme
- 11 mark for correctly marking option (D) Leucocytes/Antigens.
Hint
Remember: leucocytes are the body's defenders; antigens are the foreign invaders they attack; antibodies are the weapons the body makes to fight antigens.
Quick Oral Answer
Leucocytes are the white blood cells that identify and destroy antigens, the foreign bodies such as viruses that threaten the body — this is how chronic stress weakening leucocyte function increases illness risk.
Analysis & Explanation
This question tests basic immunology terms used to explain how psychological stress affects immune functioning (psychoneuroimmunology).
Why (D) is correct
- Leucocytes (white blood cells) are the immune system's primary defensive cells; they detect and eliminate harmful foreign substances.
- Antigens are the foreign substances (such as viruses, bacteria, or toxins) that trigger an immune response and are targeted by leucocytes.
- The correct order — Leucocytes first, then Antigens — precisely fits both blanks in the sentence.
Why the other options are wrong
- (A) 'Antigens/Leucocytes' reverses the terms — antigens are the foreign invaders, not the white blood cells performing the identifying.
- (B) 'Leucocytes/Antibodies' correctly identifies white blood cells as leucocytes but wrongly calls the foreign bodies 'antibodies', which are actually protective proteins PRODUCED BY the immune system to fight antigens, not the foreign invaders themselves.
- (C) 'Antigens/Antibodies' mislabels the white blood cells as antigens and confuses foreign invaders with the body's own defensive antibodies.
Common Mistakes
- 1Confusing antigens (foreign invaders) with antibodies (the body's own protective proteins made in response to antigens).
- 2Reversing the order of the two blanks, calling the white blood cells 'antigens' instead of 'leucocytes'.
Interesting Facts
Chronic psychological stress has been shown to reduce leucocyte activity, which is why highly stressed individuals often fall ill more frequently — a finding central to the field of psychoneuroimmunology.
The word 'leucocyte' comes from Greek 'leukos' (white) and 'kytos' (cell), literally meaning 'white cell'.
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Frequently Asked Questions
What is the difference between antigens and antibodies?
Antigens are foreign substances (like viruses or bacteria) that invade the body and trigger an immune response; antibodies are proteins produced by the immune system specifically to identify and neutralise those antigens.
How does stress affect the immune system?
Chronic stress increases cortisol and other stress hormones that suppress leucocyte (white blood cell) function, reducing the body's ability to fight antigens and increasing vulnerability to infections and illness.