Question

Which of the following statements are incorrect regarding T and B lymphocytes?
I) T-lymphocytes are produced in the thymus.
II) T-lymphocytes mature in the thymus.
III) B-lymphocytes proliferate in the spleen.
IV) B-lymphocytes mature in the thymus.

• A. I and II
• B. I, II and III
• C. I, II and IV
• D. I and IV

Answer 1

The correct option is D I and IV

Lymphocytes are the white blood cells with a non-granular cytoplasm and can provide immunity against specific foreign substances in the body. They are major mediators of antigen specific acquired immunity that is developed in an individual when he/she encounters various antigens (foreign bodies that are capable of triggering an immunological response) in his/her lifetime.

All lymphocytes are produced in the bone marrow (soft spongy tissue present in the cavity of long bones) from pluripotent stem cells which have the ability to divide and differentiate into any type of blood cell.

After formation, the lymphocytes undergo maturation in the primary lymphoid organs. Based on their site of maturation, lymphocytes have been categorised as:

• B-lymphocytes that mature in the bone marrow
• T-lymphocytes that mature in the thymus (lobed organ located near the heart and beneath the breastbone)

These lymphocytes migrate to the organs like spleen, tonsils, lymph nodes, etc, after maturation. There they interact with trapped antigens and proliferate by dividing and differentiating into different cell types (effector cells and memory cells) that have different immunological functions.

B-lymphocytes interact with antigens to divide and differentiate into plasma cells that produce antigen specific antibodies. Interaction between the antigen and the antibody might result in the destruction or elimination of the antigen by the immune system.

T-lymphocytes interact with antigens, divide and differentiate to form different types of T cells (effector cells and memory cells). Some of these newly formed T cells act against the antigens.

Thus, statements II and III are correct whereas statements I and IV are incorrect.
Figure: Maturation of T and B cells