Plasma cell 926954 222630618 2008-06-30T10:17:24Z Gustavocarra 5530698 interwiki [[Image:Plasmacell.jpg|thumb|Plasma cell]] '''Plasma cells''' (also called '''plasma B cells''' or '''plasmocytes''') are cells of the [[immune system]] that secrete large amounts of [[antibody|antibodies]]. They differentiate from [[B lymphocyte|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 [[lysosome]]s 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 cell]]s. Plasma B cells originate in the [[bone marrow]], then travel to the [[spleen]] or [[lymph nodes]] to secrete antibodies (approximately 10,000 per second). During the initial stages of an immune response the lifespan of plasma cells is very short, typically only a few days to weeks. 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 [[cytokine]]s, from other immune system cells, such as [[macrophage]]s and [[T helper cell]]s. 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 [[cell nucleus|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 [[centriole]]s ([http://www.stritch.luc.edu/lumen/meded/Histo/HistoImages/hl2A-33.jpg EM 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 [[cellular differentiation|differentiation]] from lymphocytes to plasma cells. The result is a low serum antibody level and risk of infections. ==External links== * {{BUHistology|21001loa}} * {{eMedicineDictionary|plasma+cell}} * {{Dorlands|c_18|12224615}} * [http://www.wadsworth.org/chemheme/heme/microscope/plasmacell.htm Histology at wadsworth.org] {{Cell-biology-stub}} {{Blood}} {{Immune system}} [[Category:Lymphocytes]] [[ca:Plasmòcit]] [[de:Plasmazelle]] [[es:Célula plasmática]] [[fr:Plasmocyte]] [[ko:플라즈마 세포]] [[it:Plasmacellula]] [[lt:Plazminės ląstelės]] [[nl:Plasmacel]] [[ja:形質細胞]] [[pl:Komórka plazmatyczna]] [[pt:Plasmócito]] [[sk:Plazmatická bunka]] [[sr:Плазмоцит]] [[sv:Plasmacell]] [[tr:Plazma hücresi]] [[zh:浆细胞]]