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تسجيل

Development of Lymphocytes

المؤلف:  Abbas, A. K., Lichtman, A. H., Pillai, S., & Henrickson, S. E.

المصدر:  Cellular and Molecular Immunology (2026)

الجزء والصفحة:  11E, P25

2026-03-23

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Lymphocytes, like all blood cells, arise after birth from stem cells in the bone marrow. The origin of lymphocytes from bone marrow progenitors was first demonstrated by experiments with radiation-induced bone marrow chimeras. Lymphocytes and their precursors are radiosensitive and are killed by high doses of γ-irradiation. If a mouse of one inbred strain is irradiated and then injected with bone marrow cells or small numbers of HSCs of another strain that can be distinguished from the host, all the lymphocytes that develop subsequently are derived from the bone marrow cells or HSCs of the donor. Such approaches have proven useful for examining the maturation of lymphocytes and other blood cells.

All lymphocytes go through complex maturation stages during which they undergo somatic recombination and expression of antigen receptor genes and acquire the functional and phenotypic characteristics of mature cells (Fig. 1). The anatomic sites where the major steps in lymphocyte development occur are called the primary (or generative, or central) lymphoid organs. These include the bone marrow, where precursors of all lymphocytes arise and B cells mature, and the thymus, where T cells mature.

Fig1. Maturation of lymphocytes. Lymphocytes develop from bone marrow stem cells, mature in the generative lymphoid organs (bone marrow and thymus for B and T cells, respectively), and then circulate through the blood to secondary lymphoid organs (lymph nodes, spleen, mucosal lymphoid tissues). Fully mature T cells leave the thymus, but immature B cells leave the bone marrow and complete their maturation in secondary lymphoid organs. Naive lymphocytes may respond to foreign antigens in these secondary lymphoid tissues or return by lymphatic drainage to the blood and recirculate through other secondary lymphoid organs.