ANATOMY

Detailed explanation-1: -Both B and T lymphocytes originate in the bone marrow but only B lymphocytes mature there; T lymphocytes migrate to the thymus to undergo their maturation. Thus B lymphocytes are so-called because they are bone marrow derived, and T lymphocytes because they are thymus derived.

Detailed explanation-2: -Lymphocytes are mature, infection-fighting cells that develop from lymphoblasts, a type of blood stem cell in the bone marrow.

Detailed explanation-3: -The bone marrow is extremely important to the immune system because all the body’s blood cells (including T and B lymphocytes) originate in the bone marrow. B lymphocytes remain in the marrow to mature, while T lymphocytes travel to the thymus.

Detailed explanation-4: -Bone marrow is major organ for the development and maturation of B cells. B cells are generated from HSCs and developed in bone marrow before they egress into peripheral blood to reach peripheral lymphoid organs. Specific cellular niches for B-cell development include CXCL12-expressing cells and IL-7-expressing cells.

Detailed explanation-5: -Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity). They are the main type of cell found in lymph, which prompted the name “lymphocyte".