From which precursor do both B lymphocytes and T lymphocytes develop?

From which precursor do both B lymphocytes and T lymphocytes develop?

• A. Hematopoietic stem cells
• B. Macrophages or monocytes
• C. Mucosa-associated lymphoid tissue
• D. The fetal liver

Answer: (A)

The starting point is hematopoietic stem cells in the bone marrow. These stem cells give rise to a common lymphoid progenitor, which then differentiates into B cells in the bone marrow and T cells after they migrate to the thymus. Macrophages or monocytes come from the myeloid lineage, not the lymphoid path; mucosa-associated lymphoid tissue is a tissue where immune responses occur, not a precursor; and while the fetal liver is an embryonic site of hematopoiesis, the general source for both B and T cells in adults is hematopoietic stem cells in the bone marrow.

The starting point is hematopoietic stem cells in the bone marrow. These stem cells give rise to a common lymphoid progenitor, which then differentiates into B cells in the bone marrow and T cells after they migrate to the thymus. Macrophages or monocytes come from the myeloid lineage, not the lymphoid path; mucosa-associated lymphoid tissue is a tissue where immune responses occur, not a precursor; and while the fetal liver is an embryonic site of hematopoiesis, the general source for both B and T cells in adults is hematopoietic stem cells in the bone marrow.