Phagocytosis (from Ancient Greek φαγεῖν (phagein) 'to eat' and κύτος (kytos) 'cell') is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome . It is one type of endocytosis . A cell that performs phagocytosis is called a phagocyte .
41-397: See text Charales is an order of freshwater green algae in the division Charophyta , class Charophyceae , commonly known as stoneworts . Depending on the treatment of the genus Nitellopsis , living (extant) species are placed into either one family ( Characeae ) or two (Characeae and Feistiellaceae ). Further families are used for fossil members of the order. Linnaeus established
82-414: A group of photosynthetic, eukaryotic organisms that include species with haplobiontic and diplobiontic life cycles. The diplobiontic species, such as Ulva , follow a reproductive cycle called alternation of generations in which two multicellular forms, haploid and diploid, alternate, and these may or may not be isomorphic (having the same morphology). In haplobiontic species only the haploid generation,
123-438: A medical potential in treatment of certain forms of autoimmune disorders. Phagocytosis is used by many protists as a means of feeding, thus constituting phagotrophy. As in phagocytic immune cells, the resulting phagosome may be merged with lysosomes ( food vacuoles ) containing digestive enzymes , forming a phagolysosome . The food particles will then be digested, and the released nutrients are diffused or transported into
164-469: A multicellular gametophyte. All land plants have a diplobiontic common ancestor, and diplobiontic forms have also evolved independently within Ulvophyceae more than once (as has also occurred in the red and brown algae). Diplobiontic green algae include isomorphic and heteromorphic forms. In isomorphic algae, the morphology is identical in the haploid and diploid generations. In heteromorphic algae,
205-452: A property of leucocytes, the immune cells, was from the German zoologist Ernst Haeckel . Haeckel discovered that blood cells of sea slug, Tethys , could ingest Indian ink (or indigo ) particles. It was the first direct evidence of phagocytosis by immune cells. Haeckel reported his experiment in a 1862 monograph Die Radiolarien (Rhizopoda Radiaria): Eine Monographie. Phagocytosis
246-459: A second signal from pattern recognition receptors (PRRs) activated by attachment to pathogen-associated molecular patterns (PAMPS), which leads to NF-κB activation. Fcγ receptors recognise IgG coated targets. The main recognised part is the Fc fragment . The molecule of the receptor contain an intracellular ITAM domain or associates with an ITAM-containing adaptor molecule. ITAM domains transduce
287-468: Is a unicellular, isogamous charophycean alga group that is the closest unicellular relative to land plants. Heterothallic strains of different mating type can conjugate to form zygospores . Sex pheromones termed protoplast-release inducing proteins (glycopolypeptides) produced by mating-type (-) and mating-type (+) cells facilitate this process. The green algae, including the characean algae, have served as model experimental organisms to understand
328-502: Is highly microbicidal. Monocytes, and the macrophages that mature from them, leave blood circulation to migrate through tissues. There they are resident cells and form a resting barrier. Macrophages initiate phagocytosis by mannose receptors , scavenger receptors , Fcγ receptors and complement receptors 1, 3 and 4. Macrophages are long-lived and can continue phagocytosis by forming new lysosomes. Dendritic cells also reside in tissues and ingest pathogens by phagocytosis. Their role
369-641: Is not killing or clearance of microbes, but rather breaking them down for antigen presentation to the cells of the adaptive immune system. Receptors for phagocytosis can be divided into two categories by recognised molecules. The first, opsonic receptors, are dependent on opsonins . Among these are receptors that recognise the Fc part of bound IgG antibodies, deposited complement or receptors, that recognise other opsonins of cell or plasma origin. Non-opsonic receptors include lectin-type receptors, Dectin receptor, or scavenger receptors. Some phagocytic pathways require
410-604: Is old in evolutionary terms, being present even in invertebrates . Neutrophils , macrophages , monocytes , dendritic cells , osteoclasts and eosinophils can be classified as professional phagocytes. The first three have the greatest role in immune response to most infections. The role of neutrophils is patrolling the bloodstream and rapid migration to the tissues in large numbers only in case of infection. There they have direct microbicidal effect by phagocytosis. After ingestion, neutrophils are efficient in intracellular killing of pathogens. Neutrophils phagocytose mainly via
451-426: Is used as a means of feeding and provides the organism part or all of its nourishment, it is called phagotrophy and is distinguished from osmotrophy , which is nutrition taking place by absorption. The history of phagocytosis represents the scientific establishment of immunology as the process is the first immune response mechanism discovered and understood as such. The earliest definitive account of cell eating
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#1732772865277492-433: The (green) plants (with chloroplasts ) the red algae (with rhodoplasts) and the glaucophytes (with muroplasts). Green algae are often classified with their embryophyte descendants in the green plant clade Viridiplantae (or Chlorobionta ). Viridiplantae, together with red algae and glaucophyte algae, form the supergroup Primoplantae, also known as Archaeplastida or Plantae sensu lato . The ancestral green alga
533-648: The Chlorophyta and Charophyta / Streptophyta . The land plants ( Embryophytes ) have emerged deep in the Charophyte alga as a sister of the Zygnematophyceae . Since the realization that the Embryophytes emerged within the green algae, some authors are starting to include them. The completed clade that includes both green algae and embryophytes is monophyletic and is referred to as
574-608: The centrosome of the phagocyte and is fused with lysosomes , forming a phagolysosome and leading to degradation. Progressively, the phagolysosome is acidified, activating degradative enzymes. Degradation can be oxygen-dependent or oxygen-independent. Leukocytes generate hydrogen cyanide during phagocytosis, and can kill bacteria , fungi , and other pathogens by generating several other toxic chemicals. Some bacteria, for example Treponema pallidum , Escheria coli and Staphylococcus aureus , are able to avoid phagocytosis by several mechanisms. Following apoptosis ,
615-497: The gametophyte is multicellular. The fertilized egg cell, the diploid zygote , undergoes meiosis , giving rise to haploid cells which will become new gametophytes. The diplobiontic forms, which evolved from haplobiontic ancestors, have both a multicellular haploid generation and a multicellular diploid generation. Here the zygote divides repeatedly by mitosis and grows into a multicellular diploid sporophyte . The sporophyte produces haploid spores by meiosis that germinate to produce
656-507: The supralittoral zone , is terrestrial and can in the Antarctic form large carpets on humid soil, especially near bird colonies. Green algae have chloroplasts that contain chlorophyll a and b , giving them a bright green colour, as well as the accessory pigments beta carotene (red-orange) and xanthophylls (yellow) in stacked thylakoids . The cell walls of green algae usually contain cellulose , and they store carbohydrate in
697-667: The Charales is Eochara wickendenii Choquette from the Middle Devonian. The family Characeae starts dominating the fossil assemblages in the Paleogene or perhaps already in the Late Cretaceous . Green algae The green algae ( sg. : green alga ) are a group of chlorophyll -containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains
738-518: The Fcγ receptors and complement receptors 1 and 3. The microbicidal effect of neutrophils is due to a large repertoire of molecules present in pre-formed granules. Enzymes and other molecules prepared in these granules are proteases, such as collagenase , gelatinase or serine proteases , myeloperoxidase , lactoferrin and antibiotic proteins. Degranulation of these into the phagosome, accompanied by high reactive oxygen species production (oxidative burst)
779-723: The Mesostigmatophyceae, Chlorokybophyceae and spirotaenia are only more conventionally basal Streptophytes. The algae of this paraphyletic group "Charophyta" were previously included in Chlorophyta, so green algae and Chlorophyta in this definition were synonyms. As the green algae clades get further resolved, the embryophytes, which are a deep charophyte branch, are included in " algae ", "green algae" and " Charophytes ", or these terms are replaced by cladistic terminology such as Archaeplastida , Plantae / Viridiplantae , and streptophytes , respectively. Green algae are
820-503: The cell surface of the macrophage such as the phosphatidylserine receptor or by soluble (free-floating) receptors such as thrombospondin 1 , GAS6 , and MFGE8 , which themselves then bind to other receptors on the macrophage such as CD36 and alpha-v beta-3 integrin . Defects in apoptotic cell clearance is usually associated with impaired phagocytosis of macrophages. Accumulation of apoptotic cell remnants often causes autoimmune disorders; thus pharmacological potentiation of phagocytosis has
861-611: The clade Viridiplantae and as the kingdom Plantae . The green algae include unicellular and colonial flagellates , most with two flagella per cell, as well as various colonial, coccoid (spherical), and filamentous forms, and macroscopic, multicellular seaweeds . There are about 22,000 species of green algae, many of which live most of their lives as single cells, while other species form coenobia (colonies), long filaments, or highly differentiated macroscopic seaweeds. A few other organisms rely on green algae to conduct photosynthesis for them. The chloroplasts in dinoflagellates of
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#1732772865277902-413: The class Chlorophyceae undergo closed mitosis in the most common form of cell division among the green algae, which occurs via a phycoplast . By contrast, charophyte green algae and land plants (embryophytes) undergo open mitosis without centrioles . Instead, a 'raft' of microtubules, the phragmoplast , is formed from the mitotic spindle and cell division involves the use of this phragmoplast in
943-478: The dying cells need to be taken up into the surrounding tissues by macrophages in a process called efferocytosis . One of the features of an apoptotic cell is the presentation of a variety of intracellular molecules on the cell surface, such as calreticulin , phosphatidylserine (from the inner layer of the plasma membrane), annexin A1 , oxidised LDL and altered glycans . These molecules are recognised by receptors on
984-427: The form of starch . All green algae have mitochondria with flat cristae . When present, paired flagella are used to move the cell. They are anchored by a cross-shaped system of microtubules and fibrous strands. Flagella are only present in the motile male gametes of charophytes bryophytes, pteridophytes, cycads and Ginkgo , but are absent from the gametes of Pinophyta and flowering plants . Members of
1025-435: The fungal species that partner in lichens cannot live on their own, while the algal species is often found living in nature without the fungus. Trentepohlia is a filamentous green alga that can live independently on humid soil, rocks or tree bark or form the photosymbiont in lichens of the family Graphidaceae . Also the macroalga Prasiola calophylla (Trebouxiophyceae) is terrestrial, and Prasiola crispa , which live in
1066-458: The genus Chara in 1753. The higher level classification of green algae was unsettled as of February 2022. AlgaeBase places Charales within the class Charophyceae and its circumscription of the division Charophyta . The number of families and their division into genera varies. As of February 2022, AlgaeBase accepts two families containing some extant species and four families containing only fossil species: AlgaeBase places
1107-584: The genus Lepidodinium , euglenids and chlorarachniophytes were acquired from ingested endosymbiont green algae, and in the latter retain a nucleomorph (vestigial nucleus). Green algae are also found symbiotically in the ciliate Paramecium , and in Hydra viridissima and in flatworms . Some species of green algae, particularly of genera Trebouxia of the class Trebouxiophyceae and Trentepohlia (class Ulvophyceae ), can be found in symbiotic associations with fungi to form lichens . In general
1148-401: The genus Nitellopsis , which has both extant and extinct species, in the family Feistiellaceae . Other sources place Nitellopsis in the family Characeae, with Feistiellaceae containing only fossil species, so that all extant species are in the family Characeae. The Interim Register of Marine and Nonmarine Genera accepts a further three extinct families: Body fossils of representatives of
1189-402: The heat of late summer. As their environment dries out, asexual V. carteri quickly die. However, they are able to escape death by switching, shortly before drying is complete, to the sexual phase of their life cycle that leads to production of dormant desiccation-resistant zygotes . Sexual development is initiated by a glycoprotein pheromone (Hallmann et al., 1998). This pheromone is one of
1230-516: The light microscope. This process is called conjugation and occurs for example in Spirogyra . Sex pheromone production is likely a common feature of green algae, although only studied in detail in a few model organisms. Volvox is a genus of chlorophytes . Different species form spherical colonies of up to 50,000 cells. One well-studied species, Volvox carteri (2,000 – 6,000 cells) occupies temporary pools of water that tend to dry out in
1271-408: The mannose receptor. Eight lectin-like domains form the extracellular part of the receptor. The ingestion mediated by the mannose receptor is distinct in molecular mechanisms from Fcγ receptor or complement receptor mediated phagocytosis. Engulfment of material is facilitated by the actin-myosin contractile system. The phagosome is the organelle formed by phagocytosis of material. It then moves toward
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1312-593: The mechanisms of the ionic and water permeability of membranes, osmoregulation , turgor regulation, salt tolerance , cytoplasmic streaming , and the generation of action potentials . Phagocytosis In a multicellular organism's immune system , phagocytosis is a major mechanism used to remove pathogens and cell debris. The ingested material is then digested in the phagosome. Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytized. Some protozoa use phagocytosis as means to obtain nutrients. Where phagocytosis
1353-587: The morphology and size are different in the gametophyte and sporophyte. Reproduction varies from fusion of identical cells ( isogamy ) to fertilization of a large non-motile cell by a smaller motile one ( oogamy ). However, these traits show some variation, most notably among the basal green algae called prasinophytes . Haploid algal cells (containing only one copy of their DNA) can fuse with other haploid cells to form diploid zygotes. When filamentous algae do this, they form bridges between cells, and leave empty cell walls behind that can be easily distinguished under
1394-417: The most potent known biological effector molecules. It can trigger sexual development at concentrations as low as 10 M. Kirk and Kirk showed that sex-inducing pheromone production can be triggered experimentally in somatic cells by heat shock . Thus heat shock may be a condition that ordinarily triggers sex-inducing pheromone in nature. The Closterium peracerosum-strigosum-littorale (C. psl) complex
1435-417: The order Charales do exist, but are rare. The fossil record of the Charales consists mostly of gyrogonites , that is, calcified fructifications or, more exactly, calcified spiral cells surrounding the oospores. It may be noted that the gyrogonites are studied by palaeontologists , but not often destroyed (using acids) during neontological research to liberate the oospores. The oldest known representative of
1476-413: The production of a cell plate . Photosynthetic eukaryotes originated following a primary endosymbiotic event, where a heterotrophic eukaryotic cell engulfed a photosynthetic cyanobacterium -like prokaryote that became stably integrated and eventually evolved into a membrane-bound organelle : the plastid . This primary endosymbiosis event gave rise to three autotrophic clades with primary plastids:
1517-496: The receptors contains a lectin-like complement-binding domain. Recognition by complement receptors is not enough to cause internalisation without additional signals. In macrophages, the CR1 , CR3 and CR4 are responsible for recognition of targets. Complement coated targets are internalised by 'sinking' into the phagocyte membrane, without any protrusions. Mannose and other pathogen-associated sugars, such as fucose , are recognised by
1558-481: The signal from the surface of the phagocyte to the nucleus. For example, activating receptors of human macrophages are FcγRI , FcγRIIA , and FcγRIII . Fcγ receptor mediated phagocytosis includes formation of protrusions of the cell called a 'phagocytic cup' and activates an oxidative burst in neutrophils. These receptors recognise targets coated in C3b , C4b and C3bi from plasma complement. The extracellular domain of
1599-963: Was a unicellular flagellate. The Viridiplantae diverged into two clades. The Chlorophyta include the early diverging prasinophyte lineages and the core Chlorophyta, which contain the majority of described species of green algae. The Streptophyta include charophytes and land plants. Below is a consensus reconstruction of green algal relationships, mainly based on molecular data. Palmophyllophyceae (prasinophyte clade VI) Prasinodermophyceae Ulvophyceae Chlorophyceae Trebouxiophyceae Chlorodendrophyceae Pedinophyceae Prasinophytes Clade VIIA Prasinophytes Clade VIIC Pycnococcaceae Nephroselmidophyceae Mamiellophyceae Pyramimonadales Mesostigmatophyceae Spirotaenia Chlorokybophyceae Streptofilum Klebsormidiophyceae Charophyceae Coleochaetophyceae Zygnematophyceae Mesotaeniaceae s.s. Embryophyta (land plants) The basal character of
1640-514: Was given by Swiss scientist Albert von Kölliker in 1849. In his report in Zeitschrift für Wissenschaftliche Zoologie, Kölliker described the feeding process of an amoeba-like alga, Actinophyrys sol (a heliozoan ) mentioning details of how the protist engulfed and swallowed (the process now called endocytosis) a small organism, that he named infusoria (a generic name for microbes at the time). The first demonstration of phagocytosis as
1681-493: Was noted by Canadian physician William Osler (1876), and later studied and named by Élie Metchnikoff (1880, 1883). Phagocytosis is one main mechanisms of the innate immune defense. It is one of the first processes responding to infection , and is also one of the initiating branches of an adaptive immune response. Although most cells are capable of phagocytosis, some cell types perform it as part of their main function. These are called 'professional phagocytes.' Phagocytosis