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T cells are one of the important types of white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell surface. T cells are born from hematopoietic stem cells, [1] found in the bone marrow.
Lymphocytes are blood cells of lymphoid (rather than the myeloid or erythroid) lineage.. Immunology pioneer Elie Metchnikoff. Lymphocytes are found in the bloodstream and originate in the bone marrow, however, they principally belong to the separate lymphatic system, which interacts with the blood circulation.
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. [1] Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), [2] [3] and innate lymphoid cells (ILCs; "innate T cell-like" cells involved in mucosal immunity and homeostasis), of which natural killer cells are an ...
Thus, although all blood cells, even lymphocytes, are normally born in the bone marrow in adults, myeloid cells in the narrowest sense of the term can be distinguished from lymphoid cells, that is, lymphocytes, which come from common lymphoid progenitor cells that give rise to B cells and T cells. [2]
In humans, circulating CD34+ hematopoietic stem cells reside in bone marrow. They produce precursors of T lymphocytes, which seed the thymus (thus becoming thymocytes) and differentiate under influence of the Notch protein and its ligands. Early, double negative thymocytes express (and can be identified by) CD2, CD5 and CD7.
In the nodules, T lymphocytes are located in the T cell zone. B lymphocytes are located in the B cell follicle. The primary B cell follicle matures in germinal centers. In the medulla are hematopoietic cells (which contribute to the formation of the blood) and stromal cells. Near the medulla is the hilum of lymph node.
Within the thymus, thymus cell lymphocytes or T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus is located in the upper front part of the chest, in the anterior superior mediastinum, behind the sternum, and in front of the heart. It is made up of two lobes, each ...
In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). [3] It is composed of hematopoietic cells, marrow adipose tissue, and supportive stromal cells. In adult humans, bone marrow is primarily located in the ribs, vertebrae, sternum, and bones of the pelvis. [4]