Myeloid tissue, in the bone marrow sense of the word myeloid ( myelo- + -oid ), is tissue of bone marrow, of bone marrow cell lineage, or resembling bone marrow, and myelogenous tissue (myelo- + -genous ) is any tissue of, or arising from, bone marrow; in these senses the terms are usually used synonymously, as for example with chronic myeloid/myelogenous leukemia.
In hematopoiesis, myeloid cells, or myelogenous cells are blood cells that arise from a progenitor cell for granulocytes, monocytes, erythrocytes, or platelets [1] [2] (the common myeloid progenitor, that is, CMP or CFU-GEMM), or in a narrower sense also often used, specifically from the lineage of the myeloblast (the myelocytes, monocytes, and their daughter types). 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] Those cells' differentiation (that is, lymphopoiesis) is not complete until they migrate to lymphatic organs such as the spleen and thymus for programming by antigen challenge. Thus, among leukocytes, the term myeloid is associated with the innate immune system, in contrast to lymphoid, which is associated with the adaptive immune system. Similarly, myelogenous usually refers to nonlymphocytic white blood cells, [3] and erythroid can often be used to distinguish "erythrocyte-related" from that sense of myeloid and from lymphoid. [4]
The word myelopoiesis has several senses in a way that parallels those of myeloid, and myelopoiesis in the narrower sense is the regulated formation specifically of myeloid leukocytes (myelocytes), allowing that sense of myelopoiesis to be contradistinguished from erythropoiesis and lymphopoiesis (even though all blood cells are normally produced in the marrow in adults).
Myeloid neoplasms always concern bone marrow cell lineage and are related to hematopoietic cells. Myeloid tissue can also be present in the liver and spleen [5] in fetuses, and sometimes even in adults as well, which leads to extramedullary hematopoiesis.
There is one other sense of myeloid that means "pertaining to the spinal cord", but it is much less commonly used. Myeloid should not be confused with myelin , referring to an insulating layer covering the axons of many neurons.
Haematopoiesis is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. In a healthy adult human, roughly ten billion to a hundred billion new blood cells are produced per day, in order to maintain steady state levels in the peripheral circulation.
Leukemia is a group of blood cancers that usually begin in the bone marrow and produce high numbers of abnormal blood cells. These blood cells are not fully developed and are called blasts or leukemia cells. Symptoms may include bleeding and bruising, bone pain, fatigue, fever, and an increased risk of infections. These symptoms occur due to a lack of normal blood cells. Diagnosis is typically made by blood tests or bone marrow biopsy.
Bone marrow is a semi-solid tissue found within the spongy portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production. 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. Bone marrow comprises approximately 5% of total body mass in healthy adult humans, such that a man weighing 73 kg (161 lbs) will have around 3.7 kg (8 lbs) of bone marrow.
Tumors of the hematopoietic and lymphoid tissues or tumours of the haematopoietic and lymphoid tissues are tumors that affect the blood, bone marrow, lymph, and lymphatic system. Because these tissues are all intimately connected through both the circulatory system and the immune system, a disease affecting one will often affect the others as well, making aplasia, myeloproliferation and lymphoproliferation closely related and often overlapping problems. While uncommon in solid tumors, chromosomal translocations are a common cause of these diseases. This commonly leads to a different approach in diagnosis and treatment of hematological malignancies. Hematological malignancies are malignant neoplasms ("cancer"), and they are generally treated by specialists in hematology and/or oncology. In some centers "hematology/oncology" is a single subspecialty of internal medicine while in others they are considered separate divisions. Not all hematological disorders are malignant ("cancerous"); these other blood conditions may also be managed by a hematologist.
Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within the (midgestational) aorta-gonad-mesonephros region, through a process known as endothelial-to-hematopoietic transition. In adults, haematopoiesis occurs in the red bone marrow, in the core of most bones. The red bone marrow is derived from the layer of the embryo called the mesoderm.
Primary myelofibrosis (PMF) is a rare bone marrow blood cancer. It is classified by the World Health Organization (WHO) as a type of myeloproliferative neoplasm, a group of cancers in which there is activation and growth of mutated cells in the bone marrow. This is most often associated with a somatic mutation in the JAK2, CALR, or MPL genes. In PMF, the bony aspects of bone marrow are remodeled in a process called osteosclerosis; in addition, fibroblast secrete collagen and reticulin proteins that are collectively referred to as (fibrosis). These two pathological processes compromise the normal function of bone marrow resulting in decreased production of blood cells such as erythrocytes, granulocytes and megakaryocytes, the latter cells responsible for the production of platelets.
The term leukemoid reaction describes an increased white blood cell count, which is a physiological response to stress or infection. It often describes the presence of immature cells such as myeloblasts or red blood cells with nuclei in the peripheral blood.
Leukopoiesis is a form of hematopoiesis in which white blood cells are formed in bone marrow located in bones in adults and hematopoietic organs in the fetus. White blood cells, indeed all blood cells, are formed from the differentiation of pluripotent hematopoietic stem cells which give rise to several cell lines with unlimited differentiation potential. These immediate cell lines, or colonies, are progenitors of red blood cells (erythrocytes), platelets (megakaryocytes), and the two main groups of WBCs, myelocytes and lymphocytes.
Granulopoiesis is a part of haematopoiesis, that leads to the production of granulocytes. A granulocyte, also referred to as a polymorphonuclear leukocyte (PMN), is a type of white blood cell that has multi lobed nuclei, usually containing three lobes, and has a significant amount of cytoplasmic granules within the cell. Granulopoiesis takes place in the bone marrow. It leads to the production of three types of mature granulocytes: neutrophils, eosinophils and basophils.
Lymphopoiesis (lĭm'fō-poi-ē'sĭs) is the generation of lymphocytes, one of the five types of white blood cells (WBCs). It is more formally known as lymphoid hematopoiesis.
Cluster of differentiation antigen 135 (CD135) also known as fms like tyrosine kinase 3, receptor-type tyrosine-protein kinase FLT3, or fetal liver kinase-2 (Flk2) is a protein that in humans is encoded by the FLT3 gene. FLT3 is a cytokine receptor which belongs to the receptor tyrosine kinase class III. CD135 is the receptor for the cytokine Flt3 ligand (FLT3L).
Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative neoplasm that features a persistent neutrophilia in peripheral blood, myeloid hyperplasia in bone marrow, hepatosplenomegaly, and the absence of the Philadelphia chromosome or a BCR/ABL fusion gene.
Homeobox protein Hox-A9 is a protein that in humans is encoded by the HOXA9 gene.
In hematology, myelopoiesis in the broadest sense of the term is the production of bone marrow and of all cells that arise from it, namely, all blood cells. In a narrower sense, myelopoiesis also refers specifically to the regulated formation of myeloid leukocytes (myelocytes), including eosinophilic granulocytes, basophilic granulocytes, neutrophilic granulocytes, and monocytes.
CFU-GEMM is a colony forming unit that generates myeloid cells. CFU-GEMM cells are the oligopotential progenitor cells for myeloid cells; they are thus also called common myeloid progenitor cells or myeloid stem cells. "GEMM" stands for granulocyte, erythrocyte, monocyte, megakaryocyte.
Megakaryocyte–erythroid progenitor cells (MEPs), among other blood cells, are generated as a result of hematopoiesis, which occurs in the bone marrow. Hematopoietic stem cells (HSC) can differentiate into one of two progenitor cells: the common lymphoid progenitor and the common myeloid progenitor. MEPs derive from the common myeloid progenitor lineage. Megakaryocyte–erythroid progenitor cells must commit to becoming either platelet-producing megakaryocytes via megakaryopoiesis or erythrocyte-producing erythroblasts via erythropoiesis. Most of the blood cells produced in the bone marrow during hematopoiesis come from megakaryocyte–erythroid progenitor cells.
White blood cells, also called immune cells or immunocytes, are cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. White blood cells include three main subtypes: granulocytes, lymphocytes and monocytes.
The haematopoietic system is the system in the body involved in the creation of the cells of blood.
Many human blood cells, such as red blood cells (RBCs), immune cells, and even platelets all originate from the same progenitor cell, the hematopoietic stem cell (HSC). As these cells are short-lived, there needs to be a steady turnover of new blood cells and the maintenance of an HSC pool. This is broadly termed hematopoiesis. This event requires a special environment, termed the hematopoietic stem cell niche, which provides the protection and signals necessary to carry out the differentiation of cells from HSC progenitors. This stem-cell niche relocates from the yolk sac to eventually rest in the bone marrow of mammals. Many pathological states can arise from disturbances in this niche environment, highlighting its importance in maintaining hematopoiesis.
Clonal hypereosinophilia, also termed primary hypereosinophilia or clonal eosinophilia, is a grouping of hematological disorders all of which are characterized by the development and growth of a pre-malignant or malignant population of eosinophils, a type of white blood cell that occupies the bone marrow, blood, and other tissues. This population consists of a clone of eosinophils, i.e. a group of genetically identical eosinophils derived from a sufficiently mutated ancestor cell.