Leucocytes within the immune system identify and destroy foreign bodies. There are several kinds of leucocytes within the immune system including:
A. Natural Killers
B. Pathogens
C. T-cells
D. Cytotoxicity
E. B-cells
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A, C, E only
The white blood cells or leucocytes of the immune system include T cells, B cells and natural killer cells.
A. Natural Killers Correct. Natural killer cells are leucocytes involved in the fight against both viruses and tumours.
B. Pathogens Incorrect. Pathogens are agents causing physical illness. They are what the immune system fights, not cells of the immune system.
C. T-cells Correct. T cells destroy invaders, and T-helper cells increase immunological activity; HIV attacks these T-helper cells.
D. Cytotoxicity Incorrect. Cytotoxicity is the cell-killing activity of natural killer cells, which stress can reduce. It is a function of a leucocyte, not a kind of leucocyte.
E. B-cells Correct. B cells are leucocytes that produce antibodies.
NCERT (2025-26): “Stress and the Immune System … There are several kinds of white blood cells or leucocytes within the immune system, including T cells, B cells and natural killer cells. T cells destroy invaders, and T-helper cells increase immunological activity. It is these T-helper cells that are attacked by the Human Immuno Deficiency Virus (HIV), the virus causing Acquired Immuno Deficiency Syndrome (AIDS). B cells produce antibodies. Natural killer cells are involved in the fight against both viruses and tumours. Stress can affect natural killer cell cytotoxicity, which is of major importance in the defence against various infections and cancer.…” “Lifestyle … Stressed individuals may be more likely to expose themselves to pathogens, which are agents causing physical illness.…” |