Humans are the only extant members of the subtribe Hominina. Together with chimpanzees and orangutans, they are part of the family Hominidae. A terrestrial animal, humans are characterized by their erect bipedal locomotion. Early hominins—particularly the australopithecines, whose brains and anatomy are in many ways more similar to ancestral non-human apes—are less referred to as "human" than hominins of the genus Homo. Several of these hominins used fire, occupied much of Eurasia, gave rise to anatomically modern Homo sapiens in Africa about 315,000 years ago. Humans began to exhibit evidence of behavioral modernity around 50,000 years ago, in several waves of migration, they ventured out of Africa and populated most of the world; the spread of the large and increasing population of humans has profoundly affected much of the biosphere and millions of species worldwide. Advantages that explain this evolutionary success include a larger brain with a well-developed neocortex, prefrontal cortex and temporal lobes, which enable advanced abstract reasoning, problem solving and culture through social learning.
Humans use tools better than any other animal. Humans uniquely use such systems of symbolic communication as language and art to express themselves and exchange ideas, organize themselves into purposeful groups. Humans create complex social structures composed of many cooperating and competing groups, from families and kinship networks to political states. Social interactions between humans have established an wide variety of values, social norms, rituals, which together undergird human society. Curiosity and the human desire to understand and influence the environment and to explain and manipulate phenomena have motivated humanity's development of science, mythology, religion and numerous other fields of knowledge. Though most of human existence has been sustained by hunting and gathering in band societies many human societies transitioned to sedentary agriculture some 10,000 years ago, domesticating plants and animals, thus enabling the growth of civilization; these human societies subsequently expanded, establishing various forms of government and culture around the world, unifying people within regions to form states and empires.
The rapid advancement of scientific and medical understanding in the 19th and 20th centuries permitted the development of fuel-driven technologies and increased lifespans, causing the human population to rise exponentially. The global human population was estimated to be near 7.7 billion in 2015. In common usage, the word "human" refers to the only extant species of the genus Homo—anatomically and behaviorally modern Homo sapiens. In scientific terms, the meanings of "hominid" and "hominin" have changed during the recent decades with advances in the discovery and study of the fossil ancestors of modern humans; the clear boundary between humans and apes has blurred, resulting in now acknowledging the hominids as encompassing multiple species, Homo and close relatives since the split from chimpanzees as the only hominins. There is a distinction between anatomically modern humans and Archaic Homo sapiens, the earliest fossil members of the species; the English adjective human is a Middle English loanword from Old French humain from Latin hūmānus, the adjective form of homō "man."
The word's use as a noun dates to the 16th century. The native English term man can refer to the species as well as to human males, or individuals of either sex; the species binomial "Homo sapiens" was coined by Carl Linnaeus in his 18th-century work Systema Naturae. The generic name "Homo" is a learned 18th-century derivation from Latin homō "man," "earthly being"; the species-name "sapiens" means "wise" or "sapient". Note that the Latin word homo refers to humans of either gender, that "sapiens" is the singular form; the genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids branch of the primates. Modern humans, defined as the species Homo sapiens or to the single extant subspecies Homo sapiens sapiens, proceeded to colonize all the continents and larger islands, arriving in Eurasia 125,000–60,000 years ago, Australia around 40,000 years ago, the Americas around 15,000 years ago, remote islands such as Hawaii, Easter Island and New Zealand between the years 300 and 1280.
The closest living relatives of humans are gorillas. With the sequencing of the human and chimpanzee genomes, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. By using the technique called a molecular clock which estimates the time required for the number of divergent mutations to accumulate between two lineages, the approximate date for the split between lineages can be calculated; the gibbons and orangutans were the first groups to split from the line leading to the h
Southern Illinois University Carbondale
Southern Illinois University is a public research university in Carbondale, United States. Founded in 1869, SIU is the oldest campus of the Southern Illinois University system; the university enrolls students from all 50 states as well as more than 100 countries. SIU offers 3 associate's, 100 bachelor's, 73 master's, 36 Ph. D programs in addition to professional degrees in architecture and medicine. An Act of the Twenty-sixth General Assembly of Illinois, approved March 9, 1869, created Southern Illinois Normal College, the second state-supported normal school in Illinois. Carbondale held the ceremony of cornerstone laying, May 17, 1870; the first historic session of Southern Illinois Normal University was a summer institute, with a first faculty of eight members and an enrollment of 53 students. It was renamed Southern Illinois University in 1947; the university continued as a teacher's college until Delyte W. Morris took office as president of the university in 1948. Morris was SIU's longest-serving president.
During his presidency, Morris transformed SIU, adding Colleges of Law and Dentistry. Southern Illinois University grew in size from 3,500 to over 24,800 students between 1950 and 1991. In 1957, a second campus of SIU was established at Edwardsville; this school, now known as Southern Illinois University Edwardsville, is an independent university within the SIU system. SIU offered the first program to provide support to students with specific learning disabilities at a college level. "Project Achieve" was founded at SIU by Barbara Cordoni Kupiec in 1978. She pursued a career in the field to help her own children and has left behind a legacy that has assisted several thousand other students in earning their degrees. In 1983, Project Achieve became the Clinical Center Achieve program when SIUC decided to institutionalize the program, making it a permanent part of the university's structure. Randy Dunn was the eighth president of the Southern Illinois University System. Dr. Dunn served as president at two other state institutions and was the state superintendent of education, appointed to that role by the Illinois State Board of Education.
His career in education includes classroom teaching, serving as principal at two school districts, serving as superintendent for two Illinois school systems, holding the rank of professor at two universities including SIUC. Dr. Dunn has served on a number of committees and task forces, he contributes to a variety of scholarly publications. Dunn received his doctorate in educational administration from the University of Illinois at Urbana-Champaign in 1991, he graduated from Illinois State University with a master's in administration and foundations in 1983, the B. S. in education in 1980. Before coming to Southern Illinois, he served as president at two other state institutions — Murray State University in Kentucky and Youngstown State University in Ohio. Before that, Dunn was the state superintendent of education, appointed to that role by the Illinois State Board of Education, he is not a stranger to the SIU System, having held the rank of professor in the Department of Educational Administration and Higher Education at SIUC.
Dunn started at the Carbondale campus as an associate professor in 1995 and was named department chair in 2000, before leaving to assume the state superintendency. During his term as chair, he taught in the joint doctoral program in educational leadership at SIU Edwardsville. Dunn began his academic career as an assistant professor in the Department of Leadership at The University of Memphis for two years before taking his faculty post at Southern Illinois University. In July 2018, Randy Dunn stepped down as SIU system president, was replaced by J. Kevin Dorsey, as interim president. Dorsey was the former dean of the SIU school of medicine. Carlo Montemagno, a professor of engineering, became chancellor of SIU Carbondale on August 15, 2017, his appointment was approved by the university's Board of Trustees July 13, 2017, at the recommendation of SIU System President Randy Dunn. Dr. Montemagno was an internationally recognized expert in nanotechnology and biomedical engineering, focusing his work on linking multiple disciplines to solve problems in areas of health and the environment.
Prior to his appointment at SIU, he founded the interdisciplinary Ingenuity Lab based at the University of Alberta in Canada. In addition to leading the lab, which connects organizations and researchers from across the Province of Alberta, he served as director of the biomaterials program for the Canadian Research Council's National Institute for Nanotechnology as well as research chair in intelligent nanosystems for the Canadian National Research Council. Dr. Montemagno passed away on October 11, 2018. SIU offers more than 300 academic degree programs across all levels: bachelors and doctoral, it offers professional programs in architecture, business and medicine. Since 1989, SIU has offered an MD/JD dual degree program, leading to the concurrent award of both degrees after completion of six years of coursework; the Carnegie Foundation categorizes Southern as: "RU/H: Research Universities." In the academic year 2013-2014 the University was awarded over $278 million in research grants, the largest of which were to the School of Medicine and the College of Science.
SIU Carbondale ranked #96 overall as a "National University" in the 2019 edition of annual college rankings by US News. At SIU, 59% of the classes have 19 or fewer students; the ratio of students to faculty is 15 to 1 and the percentage of full-time faculty is 83 percent. Additionally, the National Scie
University of South Carolina
The University of South Carolina is a public research university in Columbia, South Carolina. It has seven satellite campuses throughout the state and its main campus covers over 359 acres in downtown Columbia not far from the South Carolina State House; the university is categorized by the Carnegie Foundation for the Advancement of Teaching as having "highest research activity." It has been ranked as an "up-and-coming" university by U. S. News & World Report, its undergraduate and graduate International Business programs have ranked among the top three programs in the nation for over a decade, it houses the largest collection of Robert Burns and Scottish literature materials outside Scotland, the world's largest Ernest Hemingway collection. Founded in 1801 as South Carolina College, USC is the flagship institution of the University of South Carolina System and offers more than 350 programs of study, leading to bachelor's, master's, doctoral degrees from fourteen degree-granting colleges and schools.
The University of South Carolina has a total enrollment of 50,000 students, with over 34,000 on the main Columbia campus as of fall 2017 - making it the largest university in the Carolinas. USC has several thousand future students in feeder programs at surrounding technical colleges. Professional schools on the Columbia campus include business, law, medicine and social work; the university was founded as South Carolina College on December 19, 1801, by an act of the South Carolina General Assembly initiated by Governor John Drayton in an effort to promote harmony between the Lowcountry and the Backcountry. On January 10, 1805, having an initial enrollment of nine students, the college commenced classes with a traditional classical curriculum; the first president was theologian Reverend Jonathan Maxcy. He was an alumnus of Brown University, with an honorary degree from Harvard University. Before coming to the college, Maxcy had served as the second president of Brown and the third president of Union College.
Maxcy's tenure lasted from 1804 through 1820. When South Carolina College opened its doors in 1801, the building now known as Rutledge College was the only building on campus. Located one block southeast of the State Capitol, it served as an administrative office, academic building, residence hall, chapel. However, the master plan for the original campus called for a total of eleven buildings, all facing a large lush gathering area. In 1807, the original President's House was the next building to be erected; the building now known as DeSaussure College followed shortly thereafter, the remaining eight buildings were constructed over the next several decades. When completed, all eleven buildings formed a U-shape open to Sumter Street; this modified quadrangle became known as the Horseshoe. As with other southern universities in the antebellum period, the most important organizations for students were the two literary societies, the Clariosophic Society and the Euphradian Society; these two societies, which arose from a split in an earlier literary society known as the Philomathic, grew to encapsulate the majority of the student body from the 1820s onward.
The College became a symbol of the South in the antebellum period as its graduates were on the forefront of secession from the Union. With the generous support of the General Assembly, South Carolina College acquired a reputation as the leading institution of the South and attracted several noteworthy scholars, including Francis Lieber, Thomas Cooper, Joseph LeConte. Seventy-two students were present for classes in January 1862 and the college functioned as best it could until a call by the Confederate government for South Carolina to fill its quota of 18,000 soldiers. A system of conscription would begin on March 20 for all men between the ages of eighteen and forty-five, so on March 8 all of the students at the college volunteered for service in order to avoid the dishonor of having been conscripted. Despite the depletion of students, the professors issued a notice that the college would temporarily close and would reopen to those under eighteen; when the college reopened on March 17, only nine students showed up for classes and it became quite apparent to all that the college would not last past the end of the term in June.
On June 25 with the consent of the state government, the Confederate authorities took possession of the college buildings and converted them into a hospital. After many unsuccessful attempts to reopen the college, the trustees passed a resolution on December 2, 1863, that closed the college. By February 1865, Sherman's army had reached the outskirts of Columbia and the college was spared from destruction by the Union forces because of its use as a hospital. In addition, a company of the 25th Iowa Volunteer Infantry Regiment was stationed at the campus on February 17 to protect it from harm and to thwart off pillaging Yankee soldiers; the Union army took possession of the college on May 24, 1865, although the future for the college appeared bleak with it under military control, General John Porter Hatch sent a letter on June 19 to the remaining professors at the college that it should reopen as soon as possible. The appointment of Benjamin Franklin Perry as provisional governor of South Carolina on June 30 by President Andrew Johnson restored civilian rule to the state.
Perry reinstated the trustees to their positions and the board met on September 20 to authorize the college to reopen on the first Monday of January in 1866. In a message to the legislature in October, Perry sought to convert the college into a university because with the state in an impoverished situation, it would provide a more practical education. Little opposition deve
Immunoglobulin E is a type of antibody that has only been found in mammals. IgE is synthesised by plasma cells. Monomers of IgE consist of two heavy chains and two light chains, with the ε chain containing 4 Ig-like constant domains. IgE's main function is immunity to parasites such as helminths like Schistosoma mansoni, Trichinella spiralis, Fasciola hepatica. IgE is utilized during immune defense against certain protozoan parasites such as Plasmodium falciparum. IgE has an essential role in type I hypersensitivity, which manifests in various allergic diseases, such as allergic asthma, most types of sinusitis, allergic rhinitis, food allergies, specific types of chronic urticaria and atopic dermatitis. IgE plays a pivotal role in responses to allergens, such as: anaphylactic drugs, bee stings, antigen preparations used in desensitization immunotherapy. Although IgE is the least abundant isotype—blood serum IgE levels in a normal individual are only 0.05% of the Ig concentration, compared to 75% for the IgGs at 10 mg/ml, which are the isotypes responsible for most of the classical adaptive immune response—it is capable of triggering the most powerful inflammatory reactions.
IgE was discovered in 1966 and 1967 by two independent groups: Kimishige Ishizaka and his wife Teruko Ishizaka at the Children's Asthma Research Institute and Hospital in Denver, by S. G. O Johansson and Hans Bennich in Sweden, their joint paper was published in April 1969. IgE primes the IgE-mediated allergic response by binding to Fc receptors found on the surface of mast cells and basophils. Fc receptors are found on eosinophils, monocytes and platelets in humans. There are two types of Fcε receptors: FcεRI, the high-affinity IgE receptor FcεRII known as CD23, the low-affinity IgE receptorIgE can upregulate the expression of both types of Fcε receptors. FcεRI is expressed on mast cells and the antigen-presenting dendritic cells in both mice and humans. Binding of antigens to IgE bound by the FcεRI on mast cells causes cross-linking of the bound IgE and the aggregation of the underlying FcεRI, leading to degranulation and the secretion of several types of type 2 cytokines like IL-3 and Stem Cell Factor which both help the mast cells survive and accumulate in tissue, IL-4, IL-5 and IL-13 as well as IL-33 which in turn activate group 2-innate lymphoid cells.
Basophils, which share a common haemopoietic progenitor with mast cells, upon the cross-linking of their surface bound IgE by antigens release type 2 cytokines like interleukin-4 and interleukin-13 and other inflammatory mediators. The low-affinity receptor is always expressed on B cells. There has been an accumulating evidence in the past decade on the physiological role of IgE: this isotype has co-evolved with basophils and mast cells in the defence against parasites like helminths but may be effective in bacterial infections. Epidemiological research shows that IgE level is increased when infected by Schistosoma mansoni, Necator americanus, nematodes in humans, it is most beneficial in removal of hookworms from the lung. Although it is not yet well understood, IgE may play an important role in the immune system’s recognition of cancer, in which the stimulation of a strong cytotoxic response against cells displaying only small amounts of early cancer markers would be beneficial. If this were the case, anti-IgE treatments such as omalizumab might have some undesirable side effects.
However, a recent study, performed based on pooled analysis using comprehensive data from 67 phase I to IV clinical trials of omalizumab in various indications, concluded that a causal relationship between omalizumab therapy and malignancy is unlikely. Atopic individuals can have up to ten times the normal level of IgE in their blood. However, this may not be a requirement for symptoms to occur as has been seen in asthmatics with normal IgE levels in their blood—recent research has shown that IgE production can occur locally in the nasal mucosa. IgE that can recognise an allergen has a unique long-lived interaction with its high-affinity receptor FcεRI so that basophils and mast cells, capable of mediating inflammatory reactions, become "primed", ready to release chemicals like histamine and certain interleukins; these chemicals cause many of the symptoms we associate with allergy, such as airway constriction in asthma, local inflammation in eczema, increased mucus secretion in allergic rhinitis, increased vascular permeability, it is presumed, to allow other immune cells to gain access to tissues, but which can lead to a fatal drop in blood pressure as in anaphylaxis.
IgE is known to be elevated in various autoimmune disorders such as Lupus, Rheumatoid Arthritis & psoriasis, is theorized to be of pathogenetic importance in RA and SLE by eliciting a hypersensitivity reaction. Regulation of IgE levels through control of B cell differentiation to antibody-secreting plasma cells is thought to involve the "low-affinity" receptor FcεRII, or CD23. CD23 may allow facilitated antigen presentation, an IgE-dependent mechanism whereby B cells expressing CD23 are able to present allergen to specific T helper cells, causing the perpetuation of a Th2 response, one of the hallmarks o
Protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers – polypeptides – formed from sequences of amino acids, the monomers of the polymer. A single amino acid monomer may be called a residue indicating a repeating unit of a polymer. Proteins form by amino acids undergoing condensation reactions, in which the amino acids lose one water molecule per reaction in order to attach to one another with a peptide bond. By convention, a chain under 30 amino acids is identified as a peptide, rather than a protein. To be able to perform their biological function, proteins fold into one or more specific spatial conformations driven by a number of non-covalent interactions such as hydrogen bonding, ionic interactions, Van der Waals forces, hydrophobic packing. To understand the functions of proteins at a molecular level, it is necessary to determine their three-dimensional structure; this is the topic of the scientific field of structural biology, which employs techniques such as X-ray crystallography, NMR spectroscopy, dual polarisation interferometry to determine the structure of proteins.
Protein structures range in size from tens to several thousand amino acids. By physical size, proteins are classified as nanoparticles, between 1–100 nm. Large aggregates can be formed from protein subunits. For example, many thousands of actin molecules assemble into a microfilament. A protein undergoes reversible structural changes in performing its biological function; the alternative structures of the same protein are referred to as different conformational isomers, or conformations, transitions between them are called conformational changes. There are four distinct levels of protein structure; the primary structure of a protein refers to the sequence of amino acids in the polypeptide chain. The primary structure is held together by peptide bonds that are made during the process of protein biosynthesis; the two ends of the polypeptide chain are referred to as the carboxyl terminus and the amino terminus based on the nature of the free group on each extremity. Counting of residues always starts at the N-terminal end, the end where the amino group is not involved in a peptide bond.
The primary structure of a protein is determined by the gene corresponding to the protein. A specific sequence of nucleotides in DNA is transcribed into mRNA, read by the ribosome in a process called translation; the sequence of amino acids in insulin was discovered by Frederick Sanger, establishing that proteins have defining amino acid sequences. The sequence of a protein is unique to that protein, defines the structure and function of the protein; the sequence of a protein can be determined by methods such as Edman degradation or tandem mass spectrometry. However, it is read directly from the sequence of the gene using the genetic code, it is recommended to use the words "amino acid residues" when discussing proteins because when a peptide bond is formed, a water molecule is lost, therefore proteins are made up of amino acid residues. Post-translational modification such as phosphorylations and glycosylations are also considered a part of the primary structure, cannot be read from the gene.
For example, insulin is composed of 51 amino acids in 2 chains. One chain has 31 amino acids, the other has 20 amino acids. Secondary structure refers to regular local sub-structures on the actual polypeptide backbone chain. Two main types of secondary structure, the α-helix and the β-strand or β-sheets, were suggested in 1951 by Linus Pauling et al; these secondary structures are defined by patterns of hydrogen bonds between the main-chain peptide groups. They have a regular geometry, being constrained to specific values of the dihedral angles ψ and φ on the Ramachandran plot. Both the α-helix and the β-sheet represent a way of saturating all the hydrogen bond donors and acceptors in the peptide backbone; some parts of the protein do not form any regular structures. They should not be confused with random coil, an unfolded polypeptide chain lacking any fixed three-dimensional structure. Several sequential secondary structures may form a "supersecondary unit". Tertiary structure refers to the three-dimensional structure of monomeric and multimeric protein molecules.
The α-helixes and β-pleated-sheets are folded into a compact globular structure. The folding is driven by the non-specific hydrophobic interactions, the burial of hydrophobic residues from water, but the structure is stable only when the parts of a protein domain are locked into place by specific tertiary interactions, such as salt bridges, hydrogen bonds, the tight packing of side chains and disulfide bonds; the disulfide bonds are rare in cytosolic proteins, since the cytosol is a reducing environment. Quaternary structure is the three-dimensional structure consisting of the aggregation of two or more individual polypeptide chains that operate as a single functional unit; the resulting multimer is stabilized by the same non-covalent interactions and disulfide bonds as in tertiary structure. There are many possible quaternary structure organisations. Complexes of two or more polypeptides are called multimers, it would be called a dimer if it contains two subunits, a trimer if it contains three subunits, a tetramer if it contains four subunits, a pentamer if it contains five subunits.
The subunits are related to one another by symmetry operations, such as a 2-fold axis in a dimer. Multimers made up of identical subunits are referred to with a prefix of "homo-" and those made up of different subuni
An antibody known as an immunoglobulin, is a large, Y-shaped protein produced by plasma cells, used by the immune system to neutralize pathogens such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the pathogen, called an antigen, via the fragment antigen-binding variable region; each tip of the "Y" of an antibody contains a paratope, specific for one particular epitope on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly. Depending on the antigen, the binding may impede the biological process causing the disease or may activate macrophages to destroy the foreign substance; the ability of an antibody to communicate with the other components of the immune system is mediated via its Fc region, which contains a conserved glycosylation site involved in these interactions. The production of antibodies is the main function of the humoral immune system.
Antibodies are secreted by B cells of the adaptive immune system by differentiated B cells called plasma cells. Antibodies can occur in two physical forms, a soluble form, secreted from the cell to be free in the blood plasma, a membrane-bound form, attached to the surface of a B cell and is referred to as the B-cell receptor; the BCR is found only on the surface of B cells and facilitates the activation of these cells and their subsequent differentiation into either antibody factories called plasma cells or memory B cells that will survive in the body and remember that same antigen so the B cells can respond faster upon future exposure. In most cases, interaction of the B cell with a T helper cell is necessary to produce full activation of the B cell and, antibody generation following antigen binding. Soluble antibodies are released into the blood and tissue fluids, as well as many secretions to continue to survey for invading microorganisms. Antibodies are glycoproteins belonging to the immunoglobulin superfamily.
They constitute most of the gamma globulin fraction of the blood proteins. They are made of basic structural units—each with two large heavy chains and two small light chains. There are several different types of antibody heavy chains that define the five different types of crystallisable fragments that may be attached to the antigen-binding fragments; the five different types of Fc regions allow antibodies to be grouped into five isotypes. Each Fc region of a particular antibody isotype is able to bind to its specific Fc Receptor, thus allowing the antigen-antibody complex to mediate different roles depending on which FcR it binds; the ability of an antibody to bind to its corresponding FcR is further modulated by the structure of the glycan present at conserved sites within its Fc region. The ability of antibodies to bind to FcRs helps to direct the appropriate immune response for each different type of foreign object they encounter. For example, IgE is responsible for an allergic response consisting of mast cell degranulation and histamine release.
IgE's Fab paratope binds to allergic antigen, for example house dust mite particles, while its Fc region binds to Fc receptor ε. The allergen-IgE-FcRε interaction mediates allergic signal transduction to induce conditions such as asthma. Though the general structure of all antibodies is similar, a small region at the tip of the protein is variable, allowing millions of antibodies with different tip structures, or antigen-binding sites, to exist; this region is known as the hypervariable region. Each of these variants can bind to a different antigen; this enormous diversity of antibody paratopes on the antigen-binding fragments allows the immune system to recognize an wide variety of antigens. The large and diverse population of antibody paratope is generated by random recombination events of a set of gene segments that encode different antigen-binding sites, followed by random mutations in this area of the antibody gene, which create further diversity; this recombinational process that produces clonal antibody paratope diversity is called VJ or VJ recombination.
The antibody paratope is polygenic, made up of three genes, V, D, J. Each paratope locus is polymorphic, such that during antibody production, one allele of V, one of D, one of J is chosen; these gene segments are joined together using random genetic recombination to produce the paratope. The regions where the genes are randomly recombined together is the hyper variable region used to recognise different antigens on a clonal basis. Antibody genes re-organize in a process called class switching that changes the one type of heavy chain Fc fragment to another, creating a different isotype of the antibody that retains the antigen-specific variable region; this allows a single antibody to be used by different types of Fc receptors, expressed on different parts of the immune system. The first use of the term "antibody" occurred in a text by Paul Ehrlich; the term Antikörper appears in the conclusion of his article "Experimental Studies on Immunity", published in October 1891, which states that, "if two substances give rise to two different Antikörper they themselves must be different".
However, the term was not accepted and several other terms for antibody were proposed.
A lymphocyte is one of the subtypes of a white blood cell in a vertebrate's immune system. Lymphocytes include natural killer cells, T cells, B cells, they are the main type of cell found in lymph, which prompted the name "lymphocyte". The three major types of lymphocyte are B cells and natural killer cells. Lymphocytes can be identified by their large nucleus. T cells and B cells are the major cellular components of the adaptive immune response. T cells are involved in cell-mediated immunity, whereas B cells are responsible for humoral immunity; the function of T cells and B cells is to recognize specific "non-self" antigens, during a process known as antigen presentation. Once they have identified an invader, the cells generate specific responses that are tailored to maximally eliminate specific pathogens or pathogen-infected cells. B cells respond to pathogens by producing large quantities of antibodies which neutralize foreign objects like bacteria and viruses. In response to pathogens some T cells, called T helper cells, produce cytokines that direct the immune response, while other T cells, called cytotoxic T cells, produce toxic granules that contain powerful enzymes which induce the death of pathogen-infected cells.
Following activation, B cells and T cells leave a lasting legacy of the antigens they have encountered, in the form of memory cells. Throughout the lifetime of an animal, these memory cells will "remember" each specific pathogen encountered, are able to mount a strong and rapid response if the same pathogen is detected again. NK cells are a part of the innate immune system and play a major role in defending the host from tumors and virally infected cells. NK cells distinguish infected cells and tumors from normal and uninfected cells by recognizing changes of a surface molecule called MHC class I. NK cells are activated in response to a family of cytokines called interferons. Activated NK cells release cytotoxic granules which destroy the altered cells, they are named "natural killer cells" because they do not require prior activation in order to kill cells which are missing MHC class I. Mammalian stem cells differentiate into several kinds of blood cell within the bone marrow; this process is called haematopoiesis.
All lymphocytes originate, during this process, from a common lymphoid progenitor before differentiating into their distinct lymphocyte types. The differentiation of lymphocytes follows various pathways in a hierarchical fashion as well as in a more plastic fashion; the formation of lymphocytes is known as lymphopoiesis. B cells mature into B lymphocytes in the bursa equivalent, which in humans is the GALT, thought to be located in the Peyer's patches of the intestine, while T cells migrate to and mature in a distinct organ, called the thymus. Following maturation, the lymphocytes enter the circulation and peripheral lymphoid organs where they survey for invading pathogens and/or tumor cells; the lymphocytes involved in adaptive immunity differentiate further after exposure to an antigen. Effector lymphocytes function to eliminate the antigen, either by releasing antibodies, cytotoxic granules or by signaling to other cells of the immune system. Memory T cells remain in the peripheral tissues and circulation for an extended time ready to respond to the same antigen upon future exposure.
Microscopically, in a Wright's stained peripheral blood smear, a normal lymphocyte has a large, dark-staining nucleus with little to no eosinophilic cytoplasm. In normal situations, the coarse, dense nucleus of a lymphocyte is the size of a red blood cell; some lymphocytes show a clear perinuclear zone around the nucleus or could exhibit a small clear zone to one side of the nucleus. Polyribosomes are a prominent feature in the lymphocytes and can be viewed with an electron microscope; the ribosomes are involved in protein synthesis, allowing the generation of large quantities of cytokines and immunoglobulins by these cells. It is impossible to distinguish between B cells in a peripheral blood smear. Flow cytometry testing is used for specific lymphocyte population counts; this can be used to determine the percentage of lymphocytes that contain a particular combination of specific cell surface proteins, such as immunoglobulins or cluster of differentiation markers or that produce particular proteins.
In order to study the function of a lymphocyte by virtue of the proteins it generates, other scientific techniques like the ELISPOT or secretion assay techniques can be used. In the circulatory system, they move from lymph node to lymph node; this contrasts with macrophages. A lymphocyte count is part of a peripheral complete blood cell count and is expressed as the percentage of lymphocytes to the total number of white blood cells counted. A general increase in the number of lymphocytes is known as lymphocytosis, whereas a decrease is known as lymphocytopenia. An increase in lymphocyte concentration is a sign of a viral infection. A high lymphocyte count wi