Question

T-lymphocytes mature in
(A) Pancreas
(B) Spleen
(C) Bone marrow
(D) Thymus

Answer 1

Hint: Lymphocytes are a type of WBC. There are two types of lymphocytes: B-lymphocytes and T-lymphocytes. They are named based on where they get matured.

Complete step by step answer:
Lymphocytes constitute around 20 – 25% of the total WBCs in the blood. There are two types of lymphocytes, namely B- lymphocytes and T-lymphocytes. B lymphocytes get matured in bone marrow, whereas T lymphocytes get matured in thymus. Bone marrow and thymus are primary lymphoid organs, where maturation of lymphocytes takes place. Gaining antigen-sensitivity is the process of maturation. The immature lymphocytes get differentiated into mature functional lymphocytes. After maturation, they migrate to secondary lymphoid organs such as the spleen where the lymphocytes interact with the actual antigen.
Even though lymphocytes mature in different organs, the immature lymphocytes are produced in a single lymphoid organ called bone marrow. All the blood cells including red blood cells, thrombocytes, and different types of WBC are produced in bone marrow through a process known as haematopoiesis. B-lymphocytes mediate humoral (antibody) immune response and T-lymphocytes mediate cell mediated response.

Understanding the options one by one,
(A) Pancreas – This cannot be the correct option, as pancreas is not a lymphoid organ.
(B) Spleen – It is a secondary lymphoid organ where interaction of lymphocytes with antigen takes place.
(C) Bone marrow – It’s a primary lymphoid organ where, production of both the lymphocytes and maturation of B- lymphocytes takes place.
(D) Thymus – It’s the actual site of maturation of T-lymphocytes (immature T-lymphocytes differentiate into functional T-lymphocytes).

Hence the correct answer is option(D)

Note: Remember, production and maturation are two different terms. For B-lymphocytes, the site of production and maturation is the same (bone marrow). For T-lymphocytes, the site of production is bone marrow and the site of maturation is thymus.