White blood cells, or leukocytes, are cells of the immune system defending the body against both infectious disease and foreign materials. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor An infectious disease is a clinically evident Disease resulting from the presence of Pathogenic microbial agents including Pathogenic viruses Pathogenic Several different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a hematopoietic stem cell. Multipotent Progenitor cells can give rise to several other cell types but those types are limited in number Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of Hematopoietic stem cells (HSCs are Stem cells that give rise to all the blood cell types including Myeloid ( Monocytes and Macrophages, Neutrophils Leukocytes are found throughout the body, including the blood and lymphatic system. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells €”such as nutrients and oxygen—and transports Waste products The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. [1]
The number of leukocytes in the blood is often an indicator of disease. There are normally between 4×109 and 11×109 white blood cells in a litre of blood, making up approximately 1% of blood in a healthy adult. The litre or liter (see spelling differences) is a unit of Volume. [2] In conditions such as leukemia, the number of leukocytes is higher than normal, and in leukopenia, this number is much lower. Leukemia or leukaemia (Greek leukos λευκός, "white" aima αίμα, "blood" is a Cancer of the Blood Leukopenia (or leukocytopenia, or leucopenia, from Greek λευκό -white and πενία -deficiency is a decrease in the number of The physical properties of leukocytes, such as volume, conductivity, and granularity, may change due to activation, the presence of immature cells, or the presence of malignant leukocytes in leukemia.
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Etymology
The name "White blood cell" derives from the fact that after centrifugation of a blood sample, the white cells are found in the Buffy coat, a thin layer of nucleated cells between the sedimented red blood cells and the blood plasma, which is typically white in color. Centrifugation is a process that involves the use of the Centrifugal force for the separation of mixtures used in industry and in laboratory settings The buffy coat is the fraction of an anticoagulated Blood sample after density gradient centrifugation that contains most of the White blood cells Blood plasma is the Liquid component of Blood, in which the Blood cells are suspended The scientific term leukocyte directly reflects this description, derived from Greek leukos - white, and kytos - cell. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Blood plasma may sometimes be green if there are large amounts of neutrophils in the sample, due to the heme-containing enzyme myeloperoxidase that they produce. A heme ( American English) or haem ( British English) is a Prosthetic group that consists of an Iron atom contained in the center of Myeloperoxidase (MPO is a Peroxidase Enzyme ( most abundantly present in Neutrophil granulocytes (a subtype of White blood cells.
Types
There are several different types of white blood cells. They all have many things in common, but are all different. One primary technique to classify them is to look for the presence of granules, which allows the differentiation of cells into the categories granulocytes and agranulocytes:
- Granulocytes (polymorphonuclear leucocytes): leukocytes characterised by the presence of differently staining granules in their cytoplasm when viewed under light microscopy. In cell biology, a granule can be any structure barely visible by light microscopy Granulocytes are a category of White blood cells characterised by Agranulocytes are a category of White blood cells characterised by the absence of granules in their Cytoplasm. In cell biology, a granule can be any structure barely visible by light microscopy These granules are membrane-bound enzymes which primarily act in the digestion of endocytosed particles. A lipid bilayer or bilayer lipid membrane ( BLM) is a membrane composed of Lipid molecules (usually Phospholipids. Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane. There are three types of granulocytes: neutrophils, basophils, and eosinophils, which are named according to their staining properties. Neutrophil granulocytes, generally referred to as neutrophils, are the most abundant type of White blood cells in humans and form an essential part of the Eosinophil granulocytes, usually called eosinophils (or less commonly acidophils) are White blood cells that are one of the Immune System components
- Agranulocytes (mononuclear leucocytes): leukocytes characterized by the apparent absence of granules in their cytoplasm. In cell biology, a granule can be any structure barely visible by light microscopy The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. Although the name implies a lack of granules these cells do contain non-specific azurophilic granules, which are lysosomes [3]. Azurophil is the term used to refer to objects that are readily Staining with an azure Dye. The cells include lymphocytes, monocytes, and macrophages. A lymphocyte is a type of White blood cell in the Vertebrate Immune system. Monocyte is a type of Leukocyte, part of the Human body 's Immune system. Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that
Overview table
| Type | Microscopic Appearance | Diagram | Approx. % in adults[4] See also: Blood values | Diameter (μm)[4] | Main targets[2] | Nucleus[2] | Granules[2] | Lifetime[4] |
|---|---|---|---|---|---|---|---|---|
| Neutrophil |  |  | 40-75% | 10-12 | multilobed | fine, faintly pink | 6 hours-few days (days in spleen and other tissue) | |
| Eosinophil |  |  | 1-6% | 10-12 | bi-lobed | full of pink-orange (when stained) | 8-12 days (circulate for 4-5 hours) | |
| Basophil |  |  | <1% | 9-10 |
| bi- or tri-lobed | large blue | ? |
| Lymphocyte |  |  | 20-45% | 7-8 |
| deeply staining, eccentric | only NK-cells [5] | weeks to years |
| Monocyte |  |  | 2-6% | 14-17 | various | kidney shaped | none | hours-days |
| Macrophage |  |  | N/A | months-years |
Neutrophil
Neutrophils defend against bacterial or fungal infection and other very small inflammatory processes that are usually first responders to microbial infection; their activity and death in large numbers forms pus. Monocyte is a type of Leukocyte, part of the Human body 's Immune system. Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that Neutrophil granulocytes, generally referred to as neutrophils, are the most abundant type of White blood cells in humans and form an essential part of the The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Pus is a whitish-yellow yellow or yellow-brown substance produced during Inflammatory responses of the body that can be found in regions of Pyogenic bacterial They are also known as polymorphonuclear leukocytes. They have a multilobed nucleus which may appear like multiple nuclei, hence the name polymorphonuclear leukocyte. The cytoplasm may look transparent because of fine granules that are faintly pink in color. Neutrophils are very active in phagocytosing bacteria and are present in large amount in the pus of wounds. These cells are not able to renew their lysosomes used in digesting microbes and die after having phagocytosed a few pathogens.
Eosinophil
Eosinophils primarily deal with parasitic infections and an increase in them may indicate such. Eosinophil granulocytes, usually called eosinophils (or less commonly acidophils) are White blood cells that are one of the Immune System components Parasitism is a type of symbiotic relationship between Organisms of different Species. Eosinophils are also the predominant inflammatory cells in allergic reactions. The most important causes of eosinophilia include allergies such as asthma, hay fever, and hives; and also parasitic infections. Generally their nucleus is bi-lobed. The cytoplasm is full of granules which assume a characteristic pink-orange color with eosin stain.
Basophil
Basophils are chiefly responsible for allergic and antigen response by releasing the chemical histamine causing inflammation. Allergy is a disorder of the Immune system often also referred to as Atopy. An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response Histamine is a Biogenic amine involved in local immune responses as well as regulating physiological function in the gut and acting as a Neurotransmitter Inflammation ( Latin, inflamatio, to set on fire is the complex biological response of vascular tissues to harmful stimuli such as Pathogens The nucleus is bi- or tri-lobed, but it is hard to see because of the number of coarse granules which hide it. They are characterised by their large blue granules.
Lymphocyte
Lymphocytes are much more common in the lymphatic system. A lymphocyte is a type of White blood cell in the Vertebrate Immune system. Lymphocytes are distinguished by having a deeply staining nucleus which may be eccentric in location, and a relatively small amount of cytoplasm. The blood has three types of lymphocytes:
- B cells: B cells make antibodies that bind to pathogens to enable their destruction. B cells are Lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious (B cells not only make antibodies that bind to pathogens, but after an attack, some B cells will retain the ability to produce an antibody to serve as a 'memory' system. Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious )
- T cells:
- CD4+ (helper) T cells co-ordinate the immune response and are important in the defence against intracellular bacteria. T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. CD4 ( Cluster of differentiation 4 is a Glycoprotein expressed on the surface of T helper cells, Regulatory T cells, Monocytes, T helper cells (also known as effector T cells or Th cells) are a sub-group of Lymphocytes (a type of White blood cell or
- CD8+ cytotoxic T cells are able to kill virus-infected and tumor cells. CD8 ( Cluster of differentiation 8 is a transmembrane Glycoprotein that serves as a Co-receptor for the T cell receptor (TCR A cytotoxic T cell (also known as TC, CTL T-Killer cell cytolytic T cell CD8+ T-cells or killer T cell) belongs to a sub-group of T lymphocytes See also Cancer A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells (termed neoplastic
- γδ T cells possess an alternative T cell receptor as opposed to CD4+ and CD8+ αβ T cells and share characteristics of helper T cells, cytotoxic T cells and natural killer cells.
- Natural killer cells: Natural killer cells are able to kill cells of the body which are displaying a signal to kill them, as they have been infected by a virus or have become cancerous. Natural killer cells (or NK cells) are a type of Cytotoxic Lymphocyte that constitute a major component of the Innate immune system. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled
Monocyte
Monocytes share the "vacuum cleaner" (phagocytosis) function of neutrophils, but are much longer lived as they have an additional role: they present pieces of pathogens to T cells so that the pathogens may be recognized again and killed, or so that an antibody response may be mounted. Monocyte is a type of Leukocyte, part of the Human body 's Immune system. Phagocytosis is the cellular process of engulfing solid particles by the Cell membrane to form an internal Phagosome, or "food vacuole A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious Monocytes eventually leave the bloodstream to become tissue macrophages which remove dead cell debris as well as attacking microrganisms. Neither of these can be dealt with effectively by the neutrophils. Unlike neutrophils, monocytes are able to replace their lysosomal contents and are thought to have a much longer active life. They have the kidney shaped nucleus and typically agranulated. They also possess abundant cytoplasm.
Macrophage
Once monocytes move from the bloodstream out into the body tissues, they undergo changes (differentiate) allowing phagocytosis and are then known as macrophages. Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that Phagocytosis is the cellular process of engulfing solid particles by the Cell membrane to form an internal Phagosome, or "food vacuole Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that
Medications causing leukopenia
Some medications can have an impact on the number and function of white blood cells. Leukopenia is the reduction in the number of white blood cells, which may affect the overall white cell count or one of the specific populations of white blood cells. Leukopenia (or leukocytopenia, or leucopenia, from Greek λευκό -white and πενία -deficiency is a decrease in the number of For example, if the number of neutrophils is low, the condition is known as neutropenia. Neutrophil granulocytes, generally referred to as neutrophils, are the most abundant type of White blood cells in humans and form an essential part of the Neutropenia (adjective neutropenic) from Latin Prefix neutro- and Greek Suffix -πενία (deficiency is Likewise, low lymphocyte levels are termed lymphopenia. A lymphocyte is a type of White blood cell in the Vertebrate Immune system. Lymphocytopenia, or lymphopenia, is the condition of having an abnormally low level of Lymphocytes in the blood Medications which can cause leukopenia include clozapine, an antipsychotic medication with a rare adverse effect leading to the total absence of all granulocytes (neutrophils, basophils, eosinophils). Clozapine (sold as Clozaril, Leponex, Fazaclo, Froidir; Gen-Clozapine in Canada Clozaril, Denzapine, Antipsychotics are a group of Psychoactive drugs commonly but not exclusively used to treat Psychosis, which is typified by Schizophrenia. Other medications include immunosuppressive drugs, such as sirolimus, mycophenolate mofetil, tacrolimus, and cyclosporine. Immunosuppression involves an act that reduces the activation or Efficacy of the Immune system. Sirolimus ( INN) is a relatively new immunosuppressant drug used to prevent rejection in organ transplantation, and is especially useful in Kidney Mycophenolic acid ( INN) (ˌmaɪkoʊˈfɛnɒlɪk or mycophenolate is an immunosuppressant drug used to prevent rejection in Organ transplantation Tacrolimus (also FK-506 or Fujimycin) is an immunosuppressive drug whose main use is after allogenic Organ transplant to reduce the Ciclosporin (ˌsaɪkləˈspɔrən cyclosporine ( USAN) or cyclosporin (former BAN) is an Immunosuppressant drug widely Interferons used to treat multiple sclerosis, like Rebif, Avonex, and Betaseron, can also cause leukopenia. Interferons ( IFN s are natural Proteins produced by the cells of the Immune system of most Vertebrates in response to challenges by foreign agents Multiple sclerosis (abbreviated MS also known as disseminated sclerosis or encephalomyelitis disseminata) is an autoimmune condition in which the Interferon beta-1a is a drug in the Interferon family used to treat Multiple sclerosis (MS Interferon beta-1a is a drug in the Interferon family used to treat Multiple sclerosis (MS Interferon beta-1b (tradenames Betaferon, Betaseron (North America and Extavia) is a drug in the Interferon family used to treat
Fixed leukocytes
Some leukocytes migrate into the tissues of the body to take up a permanent residence at that location rather than remaining in the blood. Often these cells have specific names depending upon which tissue they settle in, such as fixed macrophages in the liver which become known as Kupffer cells. Kupffer cells, also known as Browicz-Kupffer cells, are specialized Macrophages located in the Liver that form part of the Reticuloendothelial system These cells still serve a role in the immune system.
- Histiocytes
- Dendritic cells (Although these will often migrate to local lymph nodes upon ingesting antigens)
- Mast cells
- Microglia
References
- ^ Maton, die; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. A histiocyte is a cell that is part of the human Immune system. Dendritic cells (DCs are Immune cells and form part of the Mammalian Immune system. A mast cell (or mastocyte) is a resident cell of several types of tissues and contains many granules rich in Histamine and Heparin Microglia are a type of Glial cell that acts as the first and main form of active immune defense in the Central nervous system (CNS Wright (1000008). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1.
- ^ a b c d Alberts, Bruce (2005). Leukocyte functions and percentage breakdown. Molecular Biology of the Cell. NCBI Bookshelf. Retrieved on 2007-04-14. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 43 BC - Battle of Forum Gallorum: Mark Antony, besieging Julius Caesar 's assassin Decimus Junius Brutus in
- ^ Gartner, Leslie P. (2007). Color Textbook of Histology, 3rd, SAUNDERS Elsevier, p. 225. ISBN 978-1-4160-2945-8.
- ^ a b c Daniels, Victor G. ; Wheater, Paul R. ; Burkitt, H. George (1979). Functional histology: a text and colour atlas. Edinburgh: Churchill Livingstone. ISBN 0-443-01657-7.
- ^ Semester 4 medical lectures at Uppsala University 2008 by Leif Jansson
External links
Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and booksDictionary
white blood cell
-noun
- (cytology, immunology) A type of blood cell that is involved with an immune response, or part of the immune system.
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