Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear, that is, they have varying shapes (morphology) of the nucleus (segmented, irregular; often lobed into three segments); and are referred to as polymorphonuclear leukocytes (PMN, PML, or PMNL). In common terms, polymorphonuclear granulocyte refers specifically to "neutrophil granulocytes", the most abundant of the granulocytes; the other types (eosinophils, basophils, and mast cells) have varying morphology. Granulocytes are produced via granulopoiesis in the bone marrow.
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👉 Granulocyte in the context of White blood cell
White blood cells (scientific name leukocytes), 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 entities. White blood cells are generally larger than red blood cells. They include three main subtypes: granulocytes, lymphocytes and monocytes.
All white blood cells are produced and derived from multipotent cells in the bone marrow known as hematopoietic stem cells. Leukocytes are found throughout the body, including the blood and lymphatic system. All white blood cells have nuclei, which distinguishes them from the other blood cells, the anucleated red blood cells (RBCs) and platelets. The different white blood cells are usually classified by cell lineage (myeloid cells or lymphoid cells). White blood cells are part of the body's immune system. They help the body fight infection and other diseases. Types of white blood cells are granulocytes (neutrophils, eosinophils, and basophils), and agranulocytes (monocytes, and lymphocytes (T cells and B cells)). Myeloid cells (myelocytes) include neutrophils, eosinophils, mast cells, basophils, and monocytes. Monocytes are further subdivided into dendritic cells and macrophages. Monocytes, macrophages, and neutrophils are phagocytic. Lymphoid cells (lymphocytes) include T cells (subdivided into helper T cells, memory T cells, cytotoxic T cells), B cells (subdivided into plasma cells and memory B cells), and natural killer cells. Historically, white blood cells were classified by their physical characteristics (granulocytes and agranulocytes), but this classification system is less frequently used now. Produced in the bone marrow, white blood cells defend the body against infections and disease. An excess of white blood cells is usually due to infection or inflammation. Less commonly, a high white blood cell count could indicate certain blood cancers or bone marrow disorders.
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Granulocyte in the context of Neutrophil
Neutrophils are a type of phagocytic white blood cell and part of innate immunity. More specifically, they form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in different animals. They are also known as neutrocytes, heterophils or polymorphonuclear leukocytes.
They are formed from stem cells in the bone marrow and differentiated into subpopulations of neutrophil-killers and neutrophil-cagers. They are short-lived (between 5 and 135 hours, see § Life span) and highly mobile, as they can enter parts of tissue where other cells/molecules cannot. Neutrophils may be subdivided into segmented neutrophils and banded neutrophils (or bands). They form part of the polymorphonuclear cells family (PMNs) together with basophils and eosinophils.
Granulocyte in the context of Mast cell
A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a part of the immune and neuroimmune systems. Mast cells were discovered by Friedrich von Recklinghausen and later rediscovered by Paul Ehrlich in 1877. Although best known for their role in allergy and anaphylaxis, mast cells play an important protective role as well, being intimately involved in wound healing, angiogenesis, immune tolerance, defense against pathogens, and vascular permeability in brain tumors.
The mast cell is very similar in both appearance and function to the basophil, a type of white blood cell. Although mast cells were once thought to be tissue-resident basophils, it has been shown that the two cells develop from different hematopoietic lineages and thus cannot be the same cells.
Granulocyte in the context of Basophil
Basophils are a type of white blood cell. Basophils are the least common type of granulocyte, representing about 0.5% to 1% of circulating white blood cells. They are the largest type of granulocyte. They are responsible for inflammatory reactions during immune response, as well as in the formation of acute and chronic allergic diseases, including anaphylaxis, asthma, atopic dermatitis and hay fever. They also produce compounds that coordinate immune responses, including histamine and serotonin that induce inflammation, and heparin that prevents blood clotting, although there are less than that found in mast cell granules. Mast cells were once thought to be basophils that migrated from the blood into their resident tissues (connective tissue), but they are now known to be different types of cells.
Basophils were discovered in 1879 by German physician Paul Ehrlich, who one year earlier had found a cell type present in tissues that he termed mastzellen (now mast cells). Ehrlich received the 1908 Nobel Prize in Physiology or Medicine for his discoveries.
Granulocyte in the context of Blood product
A blood product is any therapeutic substance prepared from blood, usually human blood; in some medicolegal contexts, the term refers specifically to human-blood-derived products. Blood products include whole blood, blood components, and blood plasma derivatives. Blood components include red blood cell concentrates or suspensions; platelets produced from whole blood or via apheresis; granulocytes; fresh frozen plasma; cryoprecipitates; antisera; and others. Some products for topical use, such as serum eye drops, have also been recently classified as blood components. Plasma derivatives are plasma proteins prepared under pharmaceutical manufacturing conditions, including: albumin; coagulation factor concentrates; and immunoglobulins.
Human blood and blood products come from blood donation, which can be from one person to another or from a person to themselves (such as when saving one's own blood for use after an upcoming surgical procedure).
Granulocyte in the context of Granulocyte transfusion
A granulocyte transfusion is a medical procedure in which granulocytes are infused into a person's blood. Granulocytes are a category of white blood cell that includes neutrophils, eosinophils, and basophils. Granulocyte transfusions were historically used to prevent and treat infections in people with neutropenia (an abnormally low level of neutrophils), but the practice declined in popularity in the 1980s. Interest in the procedure increased in the 1990s due to the development of more effective methods for harvesting granulocytes and a growing population of people with severe neutropenia from chemotherapy. However, the treatment's efficacy remains poorly understood and its use is controversial.
Granulocytes are most often collected through leukapheresis, a process that separates the donor's white blood cells from their red blood cells and plasma. Donors may be given corticosteroids or granulocyte colony-stimulating factor to increase their granulocyte count prior to the blood collection. Granulocytes have a short shelf life and it is recommended that they are transfused within hours of collection. Adverse effects from granulocyte transfusions include fever, chills, respiratory symptoms, transfusion-transmitted infections, and the development of antibodies against human leukocyte antigens, which can interfere with subsequent transfusions.