Question

Hematopoiesis and maturation of lymphocytes occurs in ___________.

• A. primary lymphoid organs
• B. secondary lymphoid organs
• C. tertiary lymphoid tissues
• D. lymph nodes

Answer 1

The correct option is A primary lymphoid organs

Hematopoiesis is the process by which the cellular components of blood along with blood plasma are formed. Hematopoiesis and maturation of lymphocytes occur in primary lymphoid organs like thymus and bone marrow. Hence option a is correct.

The lymphocytes are divided into three major types as follows :

• B-lymphocytes
• T-lymphocytes
• NK cells (Natural killer cells)

B-lymphocytes originate and mature in bone marrow while T-lymphocytes originate in the bone marrow and move to thymus for maturation.

B-lymphocytes are responsible for providing humoral immunity by producing antibodies, while the T-lymphocytes is responsible for cell-mediated immunity.

NK cells help in killing virally infected cells and detecting and controlling early signs of cancer.


Secondary lymphoid organs are sites where mature lymphocytes can interact effectively with that antigen. Examples of secondary lymphoid organs and tissues are spleen, lymph nodes, MALT (Mucosa-associated lymphoid tissue).

Lymph nodes are encapsulated bean-shaped structures clustered at the junctions of lymphatic vessels. It is the first organised lymphoid structure to encounter antigens that enter the tissue spaces.

Tertiary lymphoid organs are abnormal lymph node-like structures that form in peripheral tissues at sites of chronic infection, transplanted organs undergoing graft rejection and some cancers.