Question

\(\beta\) - lymphocytes develop immunocompetence in the
A. Bone marrow
B. Spleen
C. Thymus
D. Lymph nodes
Choose the correct answer from the options given below

• A. A only
• B. A and B only
• C. B and C only
• D. A, C and D only

Hint:

Site of Lymphocyte Immunocompetence:
B-Cells = BONE MARROW (Mammals) Bursa of Fabricius (Birds).
T-Cells = THYMUS.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Primary vs secondary lymphoid organs: mammalian B-lymphocytes undergo antigen-independent maturation and self-tolerance in the bone marrow.
Key Formula or Approach:
\[ \text{Primary Lymphoid Organ (B-Cell Maturation)} = \text{Bone Marrow (Mammals) / Bursa of Fabricius (Birds)} \]

Step 2: Detailed Explanation:
Primary vs secondary lymphoid tissue functions:
1. Bone Marrow (A only): The primary lymphoid organ in mammals where pluripotent hematopoietic stem cells differentiate through pro-B and pre-B stages, assemble functional B-cell receptors (BCR/surface IgM), undergo central negative selection against self-antigens, and acquire full immunocompetence before migrating into the peripheral circulation.
2. Thymus (C): Primary lymphoid organ for T-lymphocyte maturation.
3. Spleen and Lymph Nodes (B, D): Secondary lymphoid organs where mature immunocompetent lymphocytes encounter foreign antigens.
Thus, B-cells develop immunocompetence in A only (Bone marrow).

Step 3: Final Answer:
Hence, B-lymphocytes develop immunocompetence in A only, matching option (A).