Lymphocyte (stained)

A lymphocyte is a type of white blood cell involved in the human body's immune system. There are two broad categories of lymphocytes, namely the large granular lymphocytes and the small lymphocytes. The 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 part of the body's defenses. 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). ... To meet Wikipedias quality standards, this article may require cleanup. ... The immune system protects the host from infection by pathogenic organisms. ... 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). ...

The NK cells are a part of the cell-mediated immunity. They can attack the host's cells that express a foreign peptide on their MHC class I surface proteins. Furthermore, the NK cells do not require activation in order to perform their cytotoxicity upon target cells. 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. ... It has been suggested that Class I MHC be merged into this article or section. ... Cytotoxicity is the quality of being poisonous to cells. ...

T cells are chiefly responsible for cell-mediated immunity whereas B cells are primarily responsible for humoral immunity (relating to antibodies). T cells are named such because these lymphocytes mature in the thymus; B cells, named for the bursa of Fabricius in which they mature in bird species, are thought to mature in the bone marrow in humans. 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). ... Schematic of antibody binding to an antigen An antibody or immunoglobulin is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... In human anatomy, the thymus is a ductless gland located in the upper anterior portion of the chest cavity. ... In birds, the bone marrow is the site of hematopoiesis and the bursa of Fabricius (Latin: Bursa cloacalis or Bursa fabricii) is a specialized organ that, as first demonstrated by Bruce Glick and later by Max Cooper and Robert Good, is necessary for B cell development. ... Grays Anatomy illustration of cells in bone marrow. ...

In the presence of an antigen, B cells can become much more metabolically active and differentiate into plasma cells, which secrete large quantities of antibodies. An antigen is a substance that stimulates an immune response, especially the production of antibodies. ... Metabolism (from Greek μεταβολισμός metabolismos) is the biochemical modification of chemical compounds in living organisms and cells. ... Plasma cells (also called plasma B cells or plasmocytes) are cells of the immune system that secrete large amounts of antibodies. ... Schematic of antibody binding to an antigen An antibody or immunoglobulin is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ...

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

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). 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. 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. ... 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. ...

It is impossible to distinguish between T cells and B cells in a peripheral blood smear. Normally, flow cytometry testing is used for specific lymphocyte population counts. When one must specifically determine the percentage of lymphocytes that produce a particular secretion (say, a specific antibody or cytokine), the ELISPOT or secretion assay techniques can be used instead. Flow cytometry is a technique for counting, examining and sorting microscopic particles suspended in a stream of fluid. ... Cytokines is a group of proteinaceous signalling compounds that like hormones and neurotransmitters are used extensively for inter-cell communication. ... ELISPOT is an immunological assay based on ELISA (Enzyme-Linked Immunosorbent Assay). ... Secretion assay is a process used in cell biology to identify cells that are secreting a particular protein (usually a cytokine). ...

The human immunodeficiency virus (HIV) hijacks and destroys T cells (specifically, CD4⁺ lymphocytes). Without this key defense, the body is susceptible to opportunistic diseases that otherwise would not kill healthy people. 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 in immunodeficient patients caused by pathogens which are incapable of causing infection in immunocompetent individuals. ...

A lymphocyte count is 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 characterized by an abnormal proliferation of blood cells, usually white blood cells (leukocytes). ... A lymphocytosis is an increase in the number of lymphocytes in the blood. ... Wikipedia does not have an article with this exact name. ...

The formation of lymphocytes is known as lymphopoiesis.

See also

A scanning electron microscope (SEM) image of normal circulating human blood. One can see red blood cells, several knobby white blood cells including lymphocytes, a monocyte, a neutrophil, and many small disc-shaped platelets.

Granulocytes Normal blood contains from 5000 to 9000 White Blood Cells (WBC’s) per cubic millimeter and 70 to 75% of them are granulocytes. These cells are formed and mature in the bone marrow and are continually being released into the blood. They make up 20 to 25% of the WBC’s. The granulocytes have multilobular nuclei and are 9 to 12 μm in diameter. (Out of the Texas Woman's University Microbiology Text Book.) link title] 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 ... Granulocytes are a category of white blood cells, characterised by the fact that all types have differently staining granules in their cytoplasm on light microscopy. ... Granulocytes are a category of white blood cells, characterised by the fact that all types have differently staining granules in their cytoplasm on light microscopy. ...

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

Agranulocytes are a category of white blood cells characterised by the absence of granules in their cytoplasm. ... 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. ... The human leukocyte antigen system (sometimes human lymphocyte antigen) (HLA) is the general name of a group of genes in the human major histocompatibility complex (MHC) region on human chromosome 6 (mouse chromosome 17) that encodes the cell-surface antigen-presenting proteins. ... 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). ...

External links

• Histology at BU 01701ooa