A scanning electron microscope (SEM) image of a single human lymphocyte.

A lymphocyte is a type of white blood cell in the vertebrate immune system. By their appearance under the light microscope, there are two broad categories of lymphocytes, namely the large granular lymphocytes and the small lymphocytes. Functionally distinct subsets of lymphocytes correlate with their appearance. Most, but not all large granular lymphocytes are more commonly known as the natural killer cells (NK cells). The small lymphocytes are the T cells and B cells. Lymphocytes play an important and integral role in the body's defenses. An average human body contains about 10^12 lymphoid cells, and the lymphoid tissue as a whole represents about 2% of the total body weight. Image File history File linksMetadata Download high-resolution version (1946x1788, 1219 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Lymphocyte Metadata This file contains additional information, probably added from the digital camera or... Image File history File linksMetadata Download high-resolution version (1946x1788, 1219 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Lymphocyte Metadata This file contains additional information, probably added from the digital camera or... SEM Cambridge S150 at Geological Institute, University Kiel, 1980 SEM opened sample chamber The scanning electron microscope (SEM) is a type of electron microscope capable of producing high-resolution images of a sample surface. ... “White Blood Cells” redirects here. ... This article does not cite any references or sources. ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... Natural NK cells are cytotoxic; small granules in their cytoplasm contain special proteins such as perforin and proteases known as granzymes. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ...

Types of lymphocytes

A stained lymphocyte surrounded by red blood cells viewed using a light microscope.

The three major types of lymphocyte are T cells, B cells and natural killer (Nk) cells Image File history File linksMetadata Download high-resolution version (856x592, 71 KB) Lymphocyte (sang humain, normal). ... Image File history File linksMetadata Download high-resolution version (856x592, 71 KB) Lymphocyte (sang humain, normal). ... “Red cell” redirects here. ... 1852 microscope Compound microscope made by John Cuff in 1750 A microscope (Greek: micron = small and scopos = aim) is an instrument for viewing objects that are too small to be seen by the naked or unaided eye. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... Natural killer cells (NK) are a type of lymphocyte (a white blood cell) and a component of nonspecific immune defense. ...

NK cells are a part of innate immune system and play a major role in defending the host from both tumours and virally infected cells. NK cells distinguish infected cells and tumours from normal and uninfected cells by recognizing alterations in levels of a surface molecule called MHC (major histocompatibility complex) class I. NK cells are activated in response to a family of cytokines called interferons. Activated NK cells release cytotoxic (cell-killing) granules which then destroy the altered cells.^[1] They were named "natural killer" because of the initial notion that they do not require prior activation in order to kill cells which are missing MHC class I. The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. ... Tumor (American English) or tumour (British English) originally means swelling, and is sometimes still used with that meaning. ... Viral may mean: Viral phenomenon Viral (pr. ... MHC I (1hsa) vs MHC II (1dlh) (more details. ... MHC class I molecules are cell surface proteins found on most cells of the body. ... Cytokines are small protein molecules that are the core of communication between immune system cells, and even between immune system cells and cells belonging to other tissue types. ... Interferons (IFNs) are natural proteins produced by the cells of the immune system of most vertebrates in response to challenges by foreign agents such as viruses, bacteria, parasites and tumor cells. ... Cytotoxicity is the quality of being poisonous to cells. ... An assortment of grains The word grain has a great many meanings, most being descriptive of a small piece or particle. ...

T cells and B-cells are the major cellular components of the adaptive immune response. T cells are involved in cell-mediated immunity whereas B cells are primarily responsible for humoral immunity (relating to antibodies). The function of T cells and B cells is to recognize specific “non-self” antigens, during a process known as antigen presentation. Once they have identified an invader, the cells generate specific responses that are tailored to maximally eliminate specific pathogens or pathogen infected cells. B cells respond to pathogens by producing large quantities of antibodies which then neutralize foreign objects like bacteria and viruses. In response to pathogens some T cells, called helper T cells produce cytokines that direct the immune response whilst other T cells, called cytotoxic T cells, produce toxic granules that induce the death of pathogen infected cells. Following activation, B cells and T cells leave a lasting legacy of the antigens they have encountered, in the form of memory cells. Throughout the lifetime of an animal these memory cells will “remember” each specific pathogen encountered, and are able to mount a strong response if the pathogen is detected again. The adaptive immune system is composed of highly specialized, systemic cells and processes that eliminate pathogenic challenges. ... Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of macrophages and NK-cells, the production of antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. ... Humoral immunity is the aspect of immunity that is mediated by secreted antibodies, produced in the cells of the B lymphocyte lineage (B cell). ... Each antibody binds to a specific antigen; an interaction similar to a lock and key. ... Antigen presentation is a process in the bodys immune system by which macrophages, dendritic cells and leukocytes capture antigens and then carry those antigens to T-cells. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... Each antibody binds to a specific antigen; an interaction similar to a lock and key. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... A helper (or TH) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class II MHC molecules found on professional antigen-presenting cells (APCs). ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... A cytotoxic T cell (also known as TC, CTL or killer T cell) belongs to a sub-group of T lymphocytes (a type of white blood cell) which are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses (or other... Granule is a generic term used for a small particle or grain. ...

Lymphocyte development

Development of blood cells

Mammalian stem cells differentiate into several kinds of blood cell within the bone marrow.^[2] This process is called haematopoiesis. All lymphocytes originate, during this process, from a common lymphoid progenitor before differentiating into their distinct lymphocyte types. The differentiation of lymphocytes follows various pathways in a hierarchical fashion as well as in a more plastic fashion. The formation of lymphocytes is known as lymphopoiesis. B cells remain in the bone marrow to mature, while T cells migrate to and mature in a distinct organ, called the thymus. Following maturation, the lymphocytes enter the circulation and peripheral lymphoid organs (e.g the spleen and lymph nodes) where they survey for invading pathogens and/or tumour cells. Image File history File links Download high-resolution version (3960x2750, 837 KB) // Created using XaraX¹. Ive drawn this schematic using the sources below as a reference. ... Image File history File links Download high-resolution version (3960x2750, 837 KB) // Created using XaraX¹. Ive drawn this schematic using the sources below as a reference. ... Mouse embryonic stem cells with fluorescent marker. ... Embryonic stem cells differentiate into cells in various body organs. ... This article does not cite any references or sources. ... Diagram that shows the development of different blood cells from hematopoietic stem cell to mature cells Haematopoiesis (from Ancient Greek: haima blood; poiesis to make) (or hematopoiesis in the United States; sometimes also haemopoiesis or hemopoiesis) is the formation of blood cellular components. ... Lymphopoiesis refers to the generation of lymphocytes, or lymphoid hematopoiesis. ... Thymus, see Thyme. ... In mammals including humans, the lymphatic vessels (or lymphatics) are a network of thin tubes that branch, like blood vessels, into tissues throughout the body. ... The spleen is an organ located in the abdomen, where it functions in the destruction of old red blood cells and holding a reservoir of blood. ... Lymph nodes are components of the lymphatic system. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ...

The lymphocytes involved in adaptive immunity (i.e. B and T cells) differentiate further after exposure to an antigen; they form effector and memory lymphocytes. Effector lymphocytes function to eliminate the antigen, either by releasing antibodies (in the case of B cells), cytotoxic granules (cytotoxic T cells) or by signaling to other cells of the immune system (helper T cells). Memory cells remain in the peripheral tissues and circulation for an extended time ready to respond to the same antigen upon future exposure.
For the server security software, see Microsoft Forefront. ... A cytotoxic T cell (also known as TC, CTL or killer T cell) belongs to a sub-group of T lymphocytes (a type of white blood cell) which are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses (or other... A T helpered cell (or TH) cell, is a T cell (a type of white blood cell or leukocyte) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class II MHC molecules found on professional antigen-presenting cells (APCs). ... Memory cell can refer to Memory B cell, a type of biological cell. ...

Characteristics

A scanning electron microscope image of normal circulating human blood showing red blood cells, several types of white blood cells including lymphocytes, a monocyte, a neutrophil and many small disc-shaped platelets.

Microscopically, in a Wright's stained peripheral blood smear, a normal lymphocyte has a large, dark-staining nucleus with little to no basophilic cytoplasm. In normal situations, the coarse, dense nucleus of a lymphocyte is approximately the size of a red blood cell (about 7 micrometres in diameter).^[2] Some lymphocytes show a clear perinuclear zone (or halo) around the nucleus or could exhibit a small clear zone to one side of the nucleus. Polyribosomes are a prominent feature in the lymphocytes and can be viewed with an electron microscope.^[2] The ribosomes are involved in protein synthesis allowing the generation of large quantities of cytokines and immunoglobulins by these cells. Image File history File links Download high-resolution version (1800x2239, 1365 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Scanning electron microscope White blood cell Platelet Neutrophil granulocyte Lymphocyte Monocyte ... Image File history File links Download high-resolution version (1800x2239, 1365 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Scanning electron microscope White blood cell Platelet Neutrophil granulocyte Lymphocyte Monocyte ... Wrights stain is a technique in histology that is used to make the differences between cells visible under light microscopy. ... A microscopic view of an abnormal blood film. ... Basophilic is a technical term used by histologists. ... This article or section does not adequately cite its references or sources. ... An electron microscope is a type of microscope that uses electrons to illuminate and create an image of a specimen. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... Schematic of antibody binding to an antigen An antibody is a protein complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ...

It is impossible to distinguish between T cells and B cells in a peripheral blood smear.^[2] Normally, flow cytometry testing is used for specific lymphocyte population counts. This can be used to specifically determine the percentage of lymphocytes that contain a particular combination of specific cell surface proteins, such as immunoglobulins or cluster of differentiation (CD) markers or that produce particular proteins (for example, cytokines). In order to study the function of a lymphocyte by virtue of the proteins it generates, other scientific techniques like the ELISPOT or secretion assay techniques can be used.^[1] Analysis of a marine sample of photosynthetic picoplankton by flow cytometry showing three different populations (Prochlorococcus, Synechococcus and picoeukaryotes) Flow cytometry is a technique for counting, examining and sorting microscopic particles suspended in a stream of fluid. ... Schematic of antibody binding to an antigen An antibody is a protein complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... The Enzyme-linked immunosorbent spot (ELISPOT) is a common method for monitoring immune responses in humans and animals. ... Secretion assay is a process used in cell biology to identify cells that are secreting a particular protein (usually a cytokine). ...

Natural killer cells (NK) are a type of lymphocyte (a white blood cell) and a component of nonspecific immune defense. ... CD16 is a Fc receptor. ... Neural Cell Adhesion Molecule (NCAM, also the cluster of differentiation CD56) is a homophilic binding glycoprotein expressed on the surface of neurons, glia and skeletal muscle. ... CD3 or CD-3 is an abbreviation with multiple meanings, including: Ford CD3 platform MediaMax CD-3, a copy protection scheme a 3-inch CD or MiniCD This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... A helper (or TH) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class II MHC molecules found on professional antigen-presenting cells (APCs). ... TCR can mean: Toronto Civic Railways Total Control Racing, a slotless track mini-car racing that lets you control your car Tottenham Court Road, a street in London which Tottenham Court Road tube station is named after TCR (music), the musical project of Robin Moulder and TC of Satiate. ... CD3 or CD-3 is an abbreviation with multiple meanings, including: Ford CD3 platform MediaMax CD-3, a copy protection scheme a 3-inch CD or MiniCD This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... CD4 (cluster of differentiation 4) is a molecule that is expressed on the surface of T helper cells (as well as regulatory T cells and dendritic cells). ... A cytotoxic T cell (also known as TC, CTL or killer T cell) belongs to a sub-group of T lymphocytes (a type of white blood cell) which are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses (or other... TCR can mean: Toronto Civic Railways Total Control Racing, a slotless track mini-car racing that lets you control your car Tottenham Court Road, a street in London which Tottenham Court Road tube station is named after TCR (music), the musical project of Robin Moulder and TC of Satiate. ... CD3 or CD-3 is an abbreviation with multiple meanings, including: Ford CD3 platform MediaMax CD-3, a copy protection scheme a 3-inch CD or MiniCD This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... CD8 (cluster of differentiation 8) is a molecule that is expressed on the surface of cytotoxic T cells. ... γδ T cells represent a small subset of T cells that possess a distinct T cell receptor (TCR) on their surface. ... TCR can mean: Toronto Civic Railways Total Control Racing, a slotless track mini-car racing that lets you control your car Tottenham Court Road, a street in London which Tottenham Court Road tube station is named after TCR (music), the musical project of Robin Moulder and TC of Satiate. ... CD3 or CD-3 is an abbreviation with multiple meanings, including: Ford CD3 platform MediaMax CD-3, a copy protection scheme a 3-inch CD or MiniCD This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... The major histocompatibility complex (MHC) is a large genomic region or gene family found in most vertebrates. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Complement component receptor 2 is a protein involved in the complement system. ...

Lymphocytes and disease

A lymphocyte count is usually part of a peripheral complete blood cell count and is expressed as percentage of lymphocytes to total white blood cells counted. An increase in lymphocytes is usually a sign of a viral infection (in some rare cases, leukemias are found through an abnormally raised lymphocyte count in an otherwise normal person). A general increase in the number of lymphocytes is known as lymphocytosis whereas a decrease is lymphocytopenia. A complete blood count (CBC) or full blood count (FBC) is a test requested by a doctor or other medical professional that gives information about the cells in a patients blood. ... Leukemia or leukaemia (see spelling differences) is a cancer of the blood or bone marrow and is characterized by an abnormal proliferation (production by multiplication) of blood cells, usually white blood cells (leukocytes). ... Lymphocytosis is an increase in the number of lymphocytes in the blood. ... Wikipedia does not have an article with this exact name. ...

A decrease in lymphocytes occurs when the human immunodeficiency virus (HIV) hijacks and destroys T cells (specifically, the CD4⁺ subgroup of T lymphocytes). Without the key defense that these T cells provide, the body becomes susceptible to opportunistic infections that otherwise would not affect healthy people. The extent of HIV progression is typically determined by measuring the percentage of CD4⁺ T cells in the patient's blood. The effects of other viruses or lymphocyte disorders can also often be estimated by counting the numbers of lymphocytes present in the blood. The human immunodeficiency virus (HIV) is a frequently mutating retrovirus that attacks the human immune system and which has been shown to cause acquired immune deficiency syndrome (AIDS). ... CD4 (cluster of differentiation 4) is a molecule that is expressed on the surface of T helper cells (as well as regulatory T cells and dendritic cells). ... Opportunistic infections are infections caused by organisms and usually do not cause disease in a person with a healthy immune system, but can affect people with a poorly functioning or suppressed immune system. ... Stop editing pages god ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ...

See also

• Addressin
• Anergy
• Complete blood count
• Cytotoxicity
• Human leukocyte antigen
• Lymphoproliferative disorders
• Reactive lymphocyte
• Secretion assay

Addressin is an extracellular protein of the endothelium of venules. ... Anergy is a theory in immunobiology in which there is a lack of reaction by the bodys defence mechanisms when foreign substances come into contact with the body. ... Schematics of shorthand for complete blood count commonly used by physicians. ... Cytotoxicity is the quality of being poisonous to cells. ... HLA region of Chromosome 6 The human leukocyte antigen system (HLA) is the name of the human major histocompatibility complex (MHC). ... Lymphoproliferative disorders (LPDs) refer to several conditions in which lymphocytes are produced in excessive quantities. ... Reactive, or atypical lymphocytes are lymphocytes that become large as a result of antigen stimulation. ... Secretion assay is a process used in cell biology to identify cells that are secreting a particular protein (usually a cytokine). ...

References

Charles Alderson Janeway, Jr. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

External links

• Histology at BU 01701ooa