Plasma cell

Plasma cells (also called plasma B cells or plasmocytes) are cells of the immune system that secrete large amounts of antibodies. They differentiate from B cells upon stimulation by CD4+ lymphocytes. The B cell acts as an antigen presenting cell (APC), consuming an offending pathogen. That pathogen gets taken up by the B cell by receptor mediated endocytosis, and broken down within these endosomes after fusion with lysosomes releasing proteolytic enzymes onto the pathogen. Once the enzymes break down the pathogen, pieces of the pathogen (which are now known as antigenic peptides) are loaded onto MHC II molecules, and presented on its extracellular surface. Once on the extracellular surface, the CD4+ T-helper lymphocyte will bind to the MHC II/Antigen molecule and cause activation of the B cell, which includes differentiation into a plasma cell, and subsequent generation of antibody against the consumed pathogen.

Overview

After dividing for around five days, mature B cells differentiate into either plasma B cells or memory B cells. Plasma B cells originate in the bone marrow, then travel to the spleen or lymph nodes to secrete antibodies (approximately 3,000 per second).Fact|date=September 2008 During the initial stages of an immune response the lifespan of plasma cells is very short, typically only 3-4 days.Fact|date=September 2008 However, following the process of affinity maturation, plasma cells can survive for months to years and continue to secrete high levels of antibodies. Memory B cells tend to be longer-lived and can therefore respond quickly upon second exposure to an antigen.

The class of antibody that a plasma cell produces depends on signals, called cytokines, from other immune system cells, such as macrophages and T helper cells. This process is called isotype-switching. For example, plasma cells will likely secrete IgG3 antibodies if they matured in the presence of the cytokine interferon-gamma. Since B cell maturation also involves somatic hypermutation, these antibodies have a very high affinity for their antigen.

Microscopic anatomy

Plasma cells are large lymphocytes with a considerable nucleus-to-cytoplasm ratio and a characteristic appearance on light microscopy. They have basophilic cytoplasm and an eccentric nucleus with heterochromatin in a characteristic cartwheel arrangement. Their cytoplasm also contains a pale zone that on electron microscopy contains an extensive Golgi apparatus and centrioles ( [http://www.stritch.luc.edu/lumen/meded/Histo/HistoImages/hl2A-33.jpgEM picture] ). Abundant rough endoplasmic reticulum combined with a well-developed Golgi apparatus makes plasma cells well-suited for secreting immunoglobulins.

Role in disease

Cancer of plasma cells is termed multiple myeloma. This condition is frequently identified because malignant plasma cells continue producing an antibody, which can be detected as a paraprotein.

Common variable immunodeficiency is thought to be due to a problem in the differentiation from lymphocytes to plasma cells. The result is a low serum antibody level and risk of infections.

External links

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* [http://www.wadsworth.org/chemheme/heme/microscope/plasmacell.htm Histology at wadsworth.org]


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Look at other dictionaries:

  • plasma cell — n a lymphocyte that is a mature antibody secreting B cell * * * a terminally differentiated cell of the B lymphocyte lineage that produces antibodies; plasma cells are oval or round with extensive rough endoplasmic reticulum, a well developed… …   Medical dictionary

  • plasma cell — [plaz′mə sīt΄] n. a type of white blood cell that produces antibodies, formed when a B cell interacts with an antigen: often called plasmacyte [plaz′mə sīt΄] …   English World dictionary

  • plasma cell — plasma cell. См. плазматическая клетка. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • plasma cell — A mature, differentiated B lymphocyte chiefly occupied with antibody synthesis and secretion; a plasma cell lives for only 5 to 7 days …   Dictionary of microbiology

  • plasma cell — A terminally differentiated antibody forming, and usually antibody secreting, cell of the B cell lineage …   Dictionary of molecular biology

  • plasma cell — plas′ma cell n. bai (mcr imv)anat. cbl an antibody secreting cell, derived from B cells, that plays a major role in antibody mediated immunity. Also called plas•ma•cyte [[t]ˈplæz məˌsaɪt[/t]] • Etymology: 1885–90 …   From formal English to slang

  • plasma cell — noun a cell that develops from a B lymphocyte in reaction to a specific antigen; found in bone marrow and sometimes in the blood • Syn: ↑plasmacyte • Hypernyms: ↑lymphocyte, ↑lymph cell • Hyponyms: ↑plasmablast …   Useful english dictionary

  • plasma cell — noun Date: 1895 a lymphocyte that is a mature antibody secreting B cell …   New Collegiate Dictionary

  • plasma cell — Anat. an antibody secreting cell, derived from B cells, that plays a major role in antibody mediated immunity. Also called plasmacyte /plaz meuh suyt /. [1885 90] * * * …   Universalium

  • plasma cell — A type of white blood cell that produces antibodies …   English dictionary of cancer terms


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