Haemopoiesis: From 2 Different Sources
The formation of blood cells and PLATELETS – a continuous process throughout life. As ageing cells are removed from the circulation, new ones, generated in the BONE MARROW, replace them.
(haematopoiesis) n. the process of production of blood cells and platelets which continues throughout life, replacing aged cells (which are removed from the circulation). In healthy adults, haemopoiesis is confined to the *bone marrow, but in embryonic life and in early infancy, as well as in certain diseases, it may occur in other sites (extramedullary haemopoiesis). See also erythropoiesis; leucopoiesis; thrombopoiesis. —haemopoietic adj.
Interleukins are lymphokines – that is, polypeptides produced by activated lymphocytes. They are involved in signalling between cells of the immune system (see IMMUNITY) and are released by several cell types, including lymphocytes. They interact to control the immune response of cells and also participate in HAEMOPOIESIS. There are seven varieties, interleukins 1 to 7. For example, interleukin 1 is produced as a result of in?ammation and stimulates the proliferation of T and B lymphocytes, enhancing the immune response by stimulating other lymphocytes and activating dormant T cells. Interleukin 2 has anti-cancer effects as it is able to activate T lymphocytes to become killer cells which destroy foreign antigens (see ANTIGEN) such as cancer cells, and this anti-cancer e?ect is being developed for clinical use. The remaining interleukins have a range of properties in cell growth and di?erentiation.... interleukins
(marrow) the tissue contained within the internal cavities of the bones. At birth, these cavities are filled entirely with blood-forming myeloid tissue (red marrow) but in later life the marrow in the limb bones is replaced by fat (yellow marrow). Samples of bone marrow may be obtained for examination by *aspiration through a stout needle or by *trephine biopsy. See also haemopoiesis.... bone marrow
n. the process of red blood cell (*erythrocyte) production, which normally occurs in the blood-forming tissue of the *bone marrow. The ultimate precursor of the red cell is the *haemopoietic stem cell, but the earliest precursor that can be identified microscopically is the *proerythroblast. This divides and passes through a series of stages of maturation termed respectively early, intermediate, and late *normoblasts, the latter finally losing its nucleus to become a mature red cell. See also haemopoiesis.... erythropoiesis
n. the process of production of *granulocytes, which normally occurs in the blood-forming tissue of the *bone marrow. Granulocytes are ultimately derived from a *haemopoietic stem cell, but the earliest precursor that can be identified microscopically is the *myeloblast. This divides and passes through a series of stages of maturation termed respectively *promyelocyte, *myelocyte, and *metamyelocyte, before becoming a mature granulocyte. See also haemopoiesis.... granulopoiesis
n. see haemopoiesis.... haematopoiesis
the cell from which all classes of blood cells are derived. It cannot be identified microscopically, but can be defined by the presence of a combination of cell-surface proteins. It can be demonstrated by *tissue culture of the blood-forming tissue of the bone marrow, as well as by growth of human haemopoietic cells in immunodeficient mice strains, such as non-obese diabetic/severe combined immunodeficient (NOD/SCID). See also haemopoiesis.... haemopoietic stem cell
a stage of *leukaemia in which there is a decrease in the number of white cells, red cells, and platelets in the blood and reduced *haemopoiesis in the bone marrow.... hypoplastic leukaemia
n. any of a family of proteins that control some aspects of haemopoiesis and the immune response (see cytokines). Many interleukins are currently characterized. Interleukin 1 (IL-1) is an inflammatory mediator. Interleukin 2 (IL-2) stimulates T lymphocytes to become *natural killer cells, active against cancer cells, and is being investigated for the treatment of cancer: recombinant interleukin 2 (aldesleukin, Proleukin), administered by subcutaneous injection, can be of benefit in the treatment of renal cell carcinoma.... interleukin
n. the process of the production of white blood cells (leucocytes), which normally occurs in the blood-forming tissue of the *bone marrow. See also granulopoiesis; haemopoiesis; lymphopoiesis; monoblast.... leucopoiesis
n. a chronic but progressive disease characterized by *fibrosis of the bone marrow, which leads to anaemia and the presence of immature red and white blood cells in the circulation. Other features include enlargement of the spleen and the presence of blood-forming (myeloid) tissue in abnormal sites, such as the spleen and liver (extramedullary *haemopoiesis). Its cause is unknown.... myelofibrosis
a tissue in the *bone marrow in which the various classes of blood cells are produced. See also haemopoiesis.... myeloid tissue
combining form denoting formation; production. Example: haemopoiesis (of blood cells).... poiesis
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