Bone marrow and thymus are primary lymphoid organs, where immature lymphocytes are:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Differentiated into mature T-lymphocytes
Primary lymphoid organs are the organs where lymphocytes arise and mature. The bone marrow and the thymus are the two of them. Here immature lymphocytes change into antigen-sensitive lymphocytes. NCERT says that both organs give the right surroundings for the development and maturation of T-lymphocytes.
(1) Developed into antibodies — Incorrect. Antibodies are made later, by activated B-lymphocytes (plasma cells), after they meet an antigen. This does not happen in the primary organs.
(2) Differentiated into mature B-lymphocytes — Incorrect. The thymus does not make B-lymphocytes, so this does not hold for both organs named in the question. NCERT’s line on these two organs speaks of T-lymphocytes.
(3) Differentiated into mature T-lymphocytes — Correct. Both the bone marrow and the thymus give the right surroundings for the development and maturation of T-lymphocytes.
(4) Modified into erythrocytes — Incorrect. Red blood cells come from stem cells in the bone marrow. Lymphocytes do not change into them.
NCERT Extract:
Immune System in the Body – …
