An opsonin is any molecule that enhances phagocytosis by marking an antigen for an immune response or marking dead cells for recycling. Opson in ancient Greece referred to the delicious side-dish of any meal, versus the sitos, or the staple of the meal. Opsonization is the molecular mechanism whereby molecules, microbes, or apoptotic cells are chemically modified to have a stronger attraction to the cell surface receptors on phagocytes and NK cells. With the antigen coated in opsonins, binding to immune cells is enhanced. Opsonization mediates phagocytosis via signal cascades from cell surface receptors. Opsonins aid the immune system in a number of ways. In a healthy individual, they mark dead and dying self cells for clearance by macrophages and neutrophils, activate complement proteins, target cells for destruction through the action of natural killer cells. All cell membranes have negative charges which makes it difficult for two cells to come close together; when opsonins bind to their targets they boost the kinetics of phagocytosis by favoring interaction between the opsonin and cell surface receptors on immune cells.
This overrides the negative charges from cell membranes. This principle holds true for clearance of pathogens as well as dying self cells. Different opsonins perform different functions. Opsonin molecules include: Antibodies are part of the adaptive immune response and are generated by B cells in response to antigen exposure; the Fab region of the antibody binds to the antigen, whereas the Fc region of the antibody binds to an Fc receptor on the phagocyte, facilitating phagocytosis. The antigen-antibody complex can activate complement through the classical complement pathway. Phagocytic cells do not have an Fc receptor for immunoglobulin M, making IgM ineffective in assisting phagocytosis alone. However, IgM is efficient at activating complement and is, considered an opsonin. IgG antibodies are capable of binding immune effector cells via their Fc domain, triggering a release of lysis products from the bound immune effector cell; this process, called antibody-dependent cellular cytotoxicity, can cause inflammation of surrounding tissues and damage to healthy cells.
The complement system is a part of the innate immune response. C3b, C4b, C1q are important complement molecules that serve as opsonins; as a part of the alternative complement pathway, the spontaneous activation of a complement cascade converts C3 to C3b, a component that can serve as an opsonin when bound to an antigen's surface. Antibodies can activate complement via the classical pathway, resulting in deposition of C3b and C4b onto the antigen surface. After C3b has bound to the surface of an antigen, it can be recognized by phagocyte receptors that signal for phagocytosis. Complement receptor 1 is expressed on all phagocytes and recognizes a number of complement opsonins, including C3b and C4b which are both parts of C3-convertase. C1q, a member of the C1 complex, is able to interact with the Fc region of antibodies. Pentraxins and ficolins are all circulating proteins that are capable of serving as opsonins, they are secreted Pattern recognition receptors. These molecules coat the microbes as opsonins and enhance neutrophil reactivity against them through a number of mechanisms.
Apoptosis is related to low tissue inflammation. A number of opsonins play a role in marking apoptotic cells for phagocytosis without a pro-inflammatory response. Members of the pentraxin family can bind to apoptotic cell membrane components like phosphatidylcholine and phosphatidylethanolamine. IgM antibodies bind to PC. Collectin molecules such as mannose-binding lectin, surfactant protein A, SP-D interact with unknown ligands on apoptotic cell membranes; when bound to the appropriate ligand these molecules interact with phagocyte receptors, enhancing phagocytosis of the marked cell. C1q is capable of binding directly to apoptotic cells, it can indirectly bind to apoptotic cells via intermediates like IgM autoantibodies, MBL, pentraxins. In both cases C1q activates complement, resulting in the cells being marked for phagocytosis by C3b and C4b. C1q is an important contributor to the clearance of apoptotic cells and debris; this process occurs in late apoptotic cells. Opsonization of apoptotic cells occurs by different mechanisms in a tissue-dependent pattern.
For example, while C1q is necessary for proper apoptotic cell clearance in the peritoneal cavity, it is not important in the lungs where SP-D plays an important role. As part of the late stage adaptive immune response and other particles are marked by IgG antibodies; these antibodies interact with Fc receptors on macrophages and neutrophils resulting in phagocytosis. The C1 complement complex can interact with the Fc region of IgG and IgM immune complexes activating the classical complement pathway and marking the antigen with C3b. C3b can spontaneously bind to pathogen surfaces through the alternative complement pathway. Furthermore, pentraxins can directly bind to C1q from the C1 complex. SP-A opsonizes a number of viral pathogens for clearance by lung alveolar macrophages. Antibody opsonization Opsonins at the US National Library of Medicine Medical Subject Headings
Reactive oxygen species
Reactive oxygen species are chemically reactive chemical species containing oxygen. Examples include peroxides, hydroxyl radical, singlet oxygen, alpha-oxygen. In a biological context, ROS are formed as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling and homeostasis. However, during times of environmental stress, ROS levels can increase dramatically; this may result in significant damage to cell structures. Cumulatively, this is known as oxidative stress; the production of ROS is influenced by stress factor responses in plants, these factors that increase ROS production include drought, chilling, nutrient deficiency, metal toxicity and UV-B radiation. ROS are generated by exogenous sources such as ionizing radiation; the reduction of molecular oxygen produces superoxide and is the precursor of most other reactive oxygen species: O2 + e− → •O−2Dismutation of superoxide produces hydrogen peroxide: 2 H+ + •O−2 + •O−2 → H2O2 + O2Hydrogen peroxide in turn may be reduced to hydroxyl radical or reduced to water: H2O2 + e− → HO− + •OH 2 H+ + 2 e− + H2O2 → 2 H2O Exogenous ROS can be produced from pollutants, smoke, xenobiotics, or radiation.
Ionizing radiation can generate damaging intermediates through the interaction with water, a process termed radiolysis. Since water comprises 55–60% of the human body, the probability of radiolysis is quite high under the presence of ionizing radiation. In the process, water loses an electron and becomes reactive. Through a three-step chain reaction, water is sequentially converted to hydroxyl radical, hydrogen peroxide, superoxide radical, oxygen; the hydroxyl radical is reactive and removes electrons from any molecule in its path, turning that molecule into a free radical and thus propagating a chain reaction. However, hydrogen peroxide is more damaging to DNA than the hydroxyl radical, since the lower reactivity of hydrogen peroxide provides enough time for the molecule to travel into the nucleus of the cell, subsequently reacting with macromolecules such as DNA. ROS are produced intracellularly through multiple mechanisms and depending on the cell and tissue types, the major sources being the "professional" producers of ROS: NADPH oxidase complexes in cell membranes, mitochondria and endoplasmic reticulum.
Mitochondria convert energy for the cell into adenosine triphosphate. The process in which ATP is produced, called oxidative phosphorylation, involves the transport of protons across the inner mitochondrial membrane by means of the electron transport chain. In the electron transport chain, electrons are passed through a series of proteins via oxidation-reduction reactions, with each acceptor protein along the chain having a greater reduction potential than the previous; the last destination for an electron along this chain is an oxygen molecule. In normal conditions, the oxygen is reduced to produce water. Superoxide is not reactive by itself, but can inactivate specific enzymes or initiate lipid peroxidation in its protonated form, hydroperoxyl HO•2; the pKa of hydroperoxyl is 4.8. Thus, at physiological pH, the majority will exist as superoxide anion. If too much damage is present in mitochondria, a cell undergoes programmed cell death. Bcl-2 proteins are layered on the surface of the mitochondria, detect damage, activate a class of proteins called Bax, which punch holes in the mitochondrial membrane, causing cytochrome C to leak out.
This cytochrome C binds to Apaf-1, or apoptotic protease activating factor-1, free-floating in the cell's cytoplasm. Using energy from the ATPs in the mitochondrion, the Apaf-1 and cytochrome C bind together to form apoptosomes; the apoptosomes activate caspase-9, another free-floating protein. The caspase-9 cleaves the proteins of the mitochondrial membrane, causing it to break down and start a chain reaction of protein denaturation and phagocytosis of the cell. Superoxide dismutases are a class of enzymes that catalyze the dismutation of superoxide into oxygen and hydrogen peroxide; as such, they are an important antioxidant defense in nearly all cells exposed to oxygen. In mammals and most chordates, three forms of superoxide dismutase are present. SOD1 is located in the cytoplasm, SOD2 in the mitochondria and SOD3 is extracellular; the first is a dimer. SOD1 and SOD3 contain zinc ions, while SOD2 has a manganese ion in its reactive centre; the genes are located on chromosomes 21, 6, 4, respectively.
The SOD-catalysed dismutation of superoxide may be written with the following half-reactions: M+ − SOD + O−2 → Mn+ − SOD + O2 Mn+ − SOD + O−2 + 2H+ → M+ − SOD + H2O2.where M = Cu. In this reaction the oxidation state of the metal cation oscillates between n and n + 1. Catalase, concentrated in peroxisomes located next to mitochondria, reacts with the hydrogen peroxide to catalyze the formation of water and oxygen. Glutathione peroxidase reduces hydrogen peroxide by transferring the energy of the reactive peroxides to a small sulfur-containing protein called glutathione; the sulfur
The Ancient Greek language includes the forms of Greek used in Ancient Greece and the ancient world from around the 9th century BCE to the 6th century CE. It is roughly divided into the Archaic period, Classical period, Hellenistic period, it is succeeded by medieval Greek. Koine is regarded as a separate historical stage of its own, although in its earliest form it resembled Attic Greek and in its latest form it approaches Medieval Greek. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects. Ancient Greek was the language of Homer and of fifth-century Athenian historians and philosophers, it has contributed many words to English vocabulary and has been a standard subject of study in educational institutions of the Western world since the Renaissance. This article contains information about the Epic and Classical periods of the language. Ancient Greek was a pluricentric language, divided into many dialects; the main dialect groups are Attic and Ionic, Aeolic and Doric, many of them with several subdivisions.
Some dialects are found in standardized literary forms used in literature, while others are attested only in inscriptions. There are several historical forms. Homeric Greek is a literary form of Archaic Greek used in the epic poems, the "Iliad" and "Odyssey", in poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic and other Classical-era dialects; the origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period, they differ in some of the detail. The only attested dialect from this period is Mycenaean Greek, but its relationship to the historical dialects and the historical circumstances of the times imply that the overall groups existed in some form. Scholars assume that major Ancient Greek period dialect groups developed not than 1120 BCE, at the time of the Dorian invasion—and that their first appearances as precise alphabetic writing began in the 8th century BCE.
The invasion would not be "Dorian" unless the invaders had some cultural relationship to the historical Dorians. The invasion is known to have displaced population to the Attic-Ionic regions, who regarded themselves as descendants of the population displaced by or contending with the Dorians; the Greeks of this period believed there were three major divisions of all Greek people—Dorians and Ionians, each with their own defining and distinctive dialects. Allowing for their oversight of Arcadian, an obscure mountain dialect, Cypriot, far from the center of Greek scholarship, this division of people and language is quite similar to the results of modern archaeological-linguistic investigation. One standard formulation for the dialects is: West vs. non-west Greek is the strongest marked and earliest division, with non-west in subsets of Ionic-Attic and Aeolic vs. Arcadocypriot, or Aeolic and Arcado-Cypriot vs. Ionic-Attic. Non-west is called East Greek. Arcadocypriot descended more from the Mycenaean Greek of the Bronze Age.
Boeotian had come under a strong Northwest Greek influence, can in some respects be considered a transitional dialect. Thessalian had come under Northwest Greek influence, though to a lesser degree. Pamphylian Greek, spoken in a small area on the southwestern coast of Anatolia and little preserved in inscriptions, may be either a fifth major dialect group, or it is Mycenaean Greek overlaid by Doric, with a non-Greek native influence. Most of the dialect sub-groups listed above had further subdivisions equivalent to a city-state and its surrounding territory, or to an island. Doric notably had several intermediate divisions as well, into Island Doric, Southern Peloponnesus Doric, Northern Peloponnesus Doric; the Lesbian dialect was Aeolic Greek. All the groups were represented by colonies beyond Greece proper as well, these colonies developed local characteristics under the influence of settlers or neighbors speaking different Greek dialects; the dialects outside the Ionic group are known from inscriptions, notable exceptions being: fragments of the works of the poet Sappho from the island of Lesbos, in Aeolian, the poems of the Boeotian poet Pindar and other lyric poets in Doric.
After the conquests of Alexander the Great in the late 4th century BCE, a new international dialect known as Koine or Common Greek developed based on Attic Greek, but with influence from other dialects. This dialect replaced most of the older dialects, although Doric dialect has survived in the Tsakonian language, spoken in the region of modern Sparta. Doric has passed down its aorist terminations into most verbs of Demotic Greek. By about the 6th century CE, the Koine had metamorphosized into Medieval Greek. Ancient Macedonian was an Indo-European language at least related to Greek, but its exact relationship is unclear because of insufficient data: a dialect of Greek; the Macedonian dialect (or l
Sir William Osler, 1st Baronet, was a Canadian physician and one of the four founding professors of Johns Hopkins Hospital. Osler created the first residency program for specialty training of physicians, he was the first to bring medical students out of the lecture hall for bedside clinical training, he has been described as the Father of Modern Medicine and one of the "greatest diagnosticians to wield a stethoscope". Osler was a person of many interests, who in addition to being a physician, was a bibliophile, historian and renowned practical joker. One of his achievements was the founding of the History of Medicine Society of the Royal Society of Medicine, London. William's great-grandfather, Edward Osler, was variously described as either a merchant seaman or a pirate. One of William's uncles, a medical officer in the Royal Navy, wrote the Life of Lord Exmouth and the poem The Voyage.. William Osler's father, Featherstone Lake Osler, the son of a shipowner at Falmouth, was a former Lieutenant in the Royal Navy who served on HMS Victory.
In 1831 Featherstone Osler was invited to serve on HMS Beagle as the science officer on Charles Darwin's historic voyage to the Galápagos Islands, but he turned it down because his father was dying. In 1833, Featherstone Osler announced; as a teenager, Featherstone Osler was aboard HMS Sappho when it was nearly destroyed by Atlantic storms and left adrift for weeks. Serving in the Navy, he was shipwrecked off Barbados. In 1837 Featherstone Osler retired from the Navy and emigrated to Canada, becoming a "saddle-bag minister" in rural Upper Canada; when Featherstone Osler and his bride, Ellen Free Picton, arrived in Canada, they were nearly shipwrecked again on Egg Island in the Gulf of Saint Lawrence. The Oslers had several children, including William, Britton Bath Osler, Sir Edmund Boyd Osler. William Osler was born in Bond Head, Canada West on July 12, 1849, raised after 1857 in Dundas, Ontario, his mother, religious, prayed that Osler would consecrate to God's service and, in 1867, her son announced he would follow his father's footsteps into the ministry.
He was educated at Trinity College School and entered Trinity College, Toronto in the autumn of 1867. At the time, however, he was becoming interested in medical science, under the influence of James Bovell, Rev. William Arthur Johnson, who both became major influences for Osler at this time, encouraging him to switch his career. In 1868, Osler enrolled in the Toronto School of Medicine, a owned institution, not part of the Medical Faculty of the University of Toronto. Osler lived with Bovell for a time, through Johnson, he was introduced to the writings of Sir Thomas Browne. Osler left the Toronto School of Medicine after being accepted to the MDCM program at McGill University Faculty of Medicine in Montreal and he received his medical degree in 1872. Following post-graduate training under Rudolf Virchow in Europe, Osler returned to the McGill University Faculty of Medicine as a professor in 1874. Here he created the first formal journal club. During this time, he showed interest in comparative pathology and is considered the first to teach veterinary pathology in North America as part of a broad understanding of disease pathogenesis.
In 1884, he was appointed Chair of Clinical Medicine at the University of Pennsylvania in Philadelphia and in 1885, was one of the seven founding members of the Association of American Physicians, a society dedicated to "the advancement of scientific and practical medicine." When he left Philadelphia in 1889, his farewell address, "Aequanimitas", was on the imperturbability and equanimity necessary for physicians. In 1889, he accepted the position as the first Physician-in-Chief of the new Johns Hopkins Hospital in Baltimore, Maryland. Shortly afterwards, in 1893, Osler was instrumental in the creation of the Johns Hopkins School of Medicine and became one of the school's first professors of medicine. Osler increased his reputation as a clinician and teacher, he presided over a expanding domain. In the hospital's first year of operation, when it had 220 beds, 788 patients were seen for a total of over 15,000 days of treatment. Sixteen years when Osler left for Oxford, over 4,200 patients were seen for a total of nearly 110,000 days of treatment.
In 1905, he was appointed to the Regius Chair of Medicine at Oxford. He was a Student of Christ Church, Oxford. In 1911, he initiated the Postgraduate Medical Association. In the same year, Osler was named a baronet in the Coronation Honours List for his contributions to the field of medicine; the largest collection of Osler's letters and papers is at the Osler Library of McGill University in Montreal and a collection of his papers is held at the United States National Library of Medicine in Bethesda, Maryland. Osler's greatest influence on medicine was to insist that students learn from seeing and talking to patients and the establishment of the medical residency; the latter idea spread across the English-speaking world and remains in place today in most teaching hospitals. Through this sy
In cell biology, a phagosome is a vesicle formed around a particle engulfed by a phagocyte via phagocytosis. Professional phagocytes include macrophages and dendritic cells. A phagosome is formed by the fusion of the cell membrane around a microorganism, a senescent cell or an apoptotic cell. Phagosomes have membrane-bound proteins to recruit and fuse with lysosomes to form mature phagolysosomes; the lysosomes contain hydrolytic enzymes and reactive oxygen species which kill and digest the pathogens. Phagosomes can form in non-professional phagocytes, but they can only engulf a smaller range of particles, do not contain ROS; the useful materials from the digested particles are moved into the cytosol, waste is removed by exocytosis. Phagosome formation is crucial for tissue homeostasis and both innate and adaptive host defense against pathogens. However, some bacteria can exploit phagocytosis as an invasion strategy, they either reproduce inside of the phagolysosome or escape into the cytoplasm before the phagosome fuses with the lysosome.
Many Mycobacteria, including Mycobacterium tuberculosis and Mycobacterium avium paratuberculosis, can manipulate the host macrophage to prevent lysosomes from fusing with phagosomes and creating mature phagolysosomes. Such incomplete maturation of the phagosome maintains an environment favorable to the pathogens inside it. Phagosomes are large enough to degrade whole bacteria, or apoptotic and senescent cells, which are >0.5μm in diameter. This means a phagosome is several orders of magnitude bigger than an endosome, measured in nanometres. Phagosomes are formed when pathogens or opsonins bind to a transmembrane receptor, which are randomly distributed on the phagocyte cell surface. Upon binding, "outside-in" signalling triggers actin polymerisation and pseudopodia formation, which surrounds and fuses behind the microorganism. Protein kinase C, phosphoinositide 3-kinase, phospholipase C are all needed for signalling and controlling particle internalisation. More cell surface receptors can bind to the particle in a zipper-like mechanism as the pathogen is surrounded, increasing the binding avidity.
Fc receptor, complement receptors, mannose receptor and Dectin-1 are phagocytic receptors, which means that they can induce phagocytosis if they are expressed in non-phagocytic cells such as fibroblasts. Other proteins such as Toll-like receptors are involved in pathogen pattern recognition and are recruited to phagosomes but do not trigger phagocytosis in non-phagocytic cells, so they are not considered phagocytic receptors. Opsonins are molecular tags such as antibodies and complements that attach to pathogens and up-regulate phagocytosis. Immunoglobulin G is the major type of antibody present in the serum, it is part of the adaptive immune system, but it links to the innate response by recruiting macrophages to phagocytose pathogens. The antibody binds to microbes with the variable Fab domain, the Fc domain binds to Fc receptors to induce phagocytosis. Complement-mediated internalisation has much less significant membrane protrusions, but the downstream signalling of both pathways converge to activate Rho GTPases.
They control actin polymerisation, required for the phagosome to fuse with endosomes and lysosomes. Other non-professional phagocytes have some degree of phagocytic activity, such as thyroid and bladder epithelial cells that can engulf erythrocytes and retinal epithelial cells that internalise retinal rods; however non-professional phagocytes do not express specific phagocytic receptors such as FcR and have a much lower rate of internalisation. Some invasive bacteria can induce phagocytosis in non-phagocytic cells to mediate host uptake. For example, Shigella can secrete toxins that alter the host cytoskeleton and enter the basolateral side of enterocytes; as the membrane of the phagosome is formed by the fusion of the plasma membrane, the basic composition of the phospholipid bilayer is the same. Endosomes and lysosomes fuse with the phagosome to contribute to the membrane when the engulfed particle is big, such as a parasite, they deliver various membrane proteins to the phagosome and modify the organelle structure.
Phagosomes can engulf artificial low-density latex beads and purified along a sucrose concentration gradient, allowing the structure and composition to be studied. By purifying phagosomes at different time points, the maturation process can be characterised. Early phagosomes are characterised by Rab5, which transition into Rab7 as the vesicle matures into late phagosomes; the nascent phagosome is not inherently bactericidal. As it matures, it becomes more acidic from pH 6.5 to pH 4, gains characteristic protein markers and hydrolytic enzymes. The different enzymes function at various optimal pH, forming a range so they each work in narrow stages of the maturation process. Enzyme activity can be fine-tuned by allowing for greater flexibility; the phagosome moves along microtubules of the cytoskeleton, fusing with endosomes and lysosomes sequentially in a dynamic "kiss-and-run" manner. This intracellular transport depends on the size of the phagosomes. Larger organelles are transported persistently from the cell periphery towards the perinuclear region whereas smaller organelles are transported more bidirectionally back and forth between cell center and cell periphery.
Vacuolar proton pumps are delivered to the phagosome to acidify the organelle compartment, creating a more hostile environment for pathogens and facilitating protein degradation. The bacterial proteins are denatured in low pH and become more
Immunoreceptor tyrosine-based activation motif
An immunoreceptor tyrosine-based activation motif is a conserved sequence of four amino acids, repeated twice in the cytoplasmic tails of certain cell surface proteins of the immune system. The motif contains a tyrosine separated from a leucine or isoleucine by any two other amino acids, giving the signature YxxL/I. Two of these signatures are separated by between 6 and 8 amino acids in the tail of the molecule. ITAMs are important for signal transduction in immune cells. Hence, they are found in the tails of important cell signaling molecules such as the CD3 and ζ-chains of the T cell receptor complex, the CD79-alpha and -beta chains of the B cell receptor complex, certain Fc receptors; the tyrosine residues within these motifs become phosphorylated following interaction of the receptor molecules with their ligands and form docking sites for other proteins involved in the signaling pathways of the cell
Innate immune system
The innate immune system is one of the two main immunity strategies found in vertebrates. The innate immune system is an older evolutionary defense strategy speaking, it is the dominant immune system response found in plants, fungi and primitive multicellular organisms; the major functions of the vertebrate innate immune system include: Recruiting immune cells to sites of infection through the production of chemical factors, including specialized chemical mediators called cytokines Activation of the complement cascade to identify bacteria, activate cells, promote clearance of antibody complexes or dead cells Identification and removal of foreign substances present in organs, tissues and lymph, by specialized white blood cells Activation of the adaptive immune system through a process known as antigen presentation Acting as a physical and chemical barrier to infectious agents. Anatomical barriers include physical and biological barriers; the epithelial surfaces form a physical barrier, impermeable to most infectious agents, acting as the first line of defense against invading organisms.
Desquamation of skin epithelium helps remove bacteria and other infectious agents that have adhered to the epithelial surfaces. Lack of blood vessels and inability of the epidermis to retain moisture, presence of sebaceous glands in the dermis provides an environment unsuitable for the survival of microbes. In the gastrointestinal and respiratory tract, movement due to peristalsis or cilia helps remove infectious agents. Mucus traps infectious agents; the gut flora can prevent the colonization of pathogenic bacteria by secreting toxic substances or by competing with pathogenic bacteria for nutrients or attachment to cell surfaces. The flushing action of tears and saliva helps prevent infection of mouth. Inflammation is one of the first responses of the immune system to irritation. Inflammation is stimulated by chemical factors released by injured cells and serves to establish a physical barrier against the spread of infection, to promote healing of any damaged tissue following the clearance of pathogens.
The process of acute inflammation is initiated by cells present in all tissues resident macrophages, dendritic cells, Kupffer cells, mast cells. These cells present receptors contained on the surface or within the cell, named pattern recognition receptors, which recognize molecules that are broadly shared by pathogens but distinguishable from host molecules, collectively referred to as pathogen-associated molecular patterns. At the onset of an infection, burn, or other injuries, these cells undergo activation and release inflammatory mediators responsible for the clinical signs of inflammation. Chemical factors produced during inflammation sensitize pain receptors, cause local vasodilation of the blood vessels, attract phagocytes neutrophils. Neutrophils trigger other parts of the immune system by releasing factors that summon additional leukocytes and lymphocytes. Cytokines produced by macrophages and other cells of the innate immune system mediate the inflammatory response; these cytokines include TNF, HMGB1, IL-1.
The inflammatory response is characterized by the following symptoms: redness of the skin, due to locally increased blood circulation. The complement system is a biochemical cascade of the immune system that helps, or “complements”, the ability of antibodies to clear pathogens or mark them for destruction by other cells; the cascade is composed of many plasma proteins, synthesized in the liver by hepatocytes. The proteins work together to: trigger the recruitment of inflammatory cells "tag" pathogens for destruction by other cells by opsonizing, or coating, the surface of the pathogen form holes in the plasma membrane of the pathogen, resulting in cytolysis of the pathogen cell, causing the death of the pathogen rid the body of neutralised antigen-antibody complexes. There are three different complement systems: Classical, Lectin Classical: starts when antibody bind to bacteria Alternative: starts "spontaneously" Lectin: starts when lectins bind to mannose on bacteriaElements of the complement cascade can be found in many non-mammalian species including plants, birds and some species of invertebrates.
All white blood cells are known as leukocytes. Leukocytes differ from other cells of the body in that they are not associated with a particular organ or tissue. Leukocytes are able to move and interact with and capture cellular debris, foreign particles, invading m