B cell
The cells of the immune system that make antibodies to invading pathogens like viruses. They form memory cells that remember the same pathogen for faster antibody production in future infections.
Latin	lymphocytus B
Code	TH H2.00.04.1.02005 TH H2.00.04.3.07002

B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by T cells). B cells are an essential component of the adaptive immune system. B cells, which are the precursors of plasma cells, are characterized by the presence of a B-cell receptor able to bind specifically an antigen. Their principal functions are to make antibodies against antigens, perform the role of antigen-presenting cells (APCs) and eventually develop into memory B cells after activation by antigen interaction. Recently, a new, suppressive function of B cells has been discovered.

The abbreviation "B", in B cell, comes from the bursa of Fabricius in birds, where they mature. In mammals, immature B cells are formed in the bone marrow, which is used as a backronym for the cells' name.^[1]

Development of B cells[link]

Immature B cells are produced in the bone marrow of most mammals. Rabbits are an exception; their B cells develop in the appendix-sacculus rotundus. After reaching the IgM+ immature stage in the bone marrow, these immature B cells migrate to secondary lymphoid tissues (such as the spleen, lymph nodes, Peyer's patches, etc.) where they are called transitional B cells, and some of these cells differentiate into mature B lymphocytes.^[2]

B cell development occurs through several stages, each stage representing a change in the genome content at the antibody loci. An antibody is composed of two identical light (L) and two identical heavy (H) chains, and the genes specifying them are found in the 'V' (Variable) region and the 'C' (Constant) region. In the heavy-chain 'V' region there are three segments; V, D and J, which recombine randomly, in a process called VDJ recombination, to produce a unique variable domain in the immunoglobulin of each individual B cell. Similar rearrangements occur for light-chain 'V' region except there are only two segments involved; V and J. The list below describes the process of immunoglobulin formation at the different stages of B cell development.

When the B cell fails in any step of the maturation process, it will die by a mechanism called apoptosis, here called clonal deletion.^[5] B cells are continuously produced in the bone marrow. When the B cell receptor, on the surface of the cell matches the detected antigens present in the body, the B cell proliferates and secretes a free form of those receptors (antibodies) with identical binding sites as the ones on the original cell surface. After activation, the cell proliferates and B memory cells would form to recognise the same antigen. This information would then be used as a part of the adaptive immune system for a more efficient and more powerful immune response for future encounters with that antigen.

B cell membrane receptors evolve and change throughout the B cell life span.^[6] TACI, BCMA and BAFF-R are present on both immature B cells and mature B cells. All of these 3 receptors may be inhibited by Belimumab. CD20 is expressed on all stages of B cell development except the first and last; it is present from pre-B cells through memory cells, but not on either pre-pro-B cells or plasma cells.^[7]

Immune Tolerance[link]

Like their fellow lymphocytes, the T cells, immature B cells are tested for auto-reactivity by the immune system before leaving the bone marrow. In the bone marrow (the central lymphoid organ), central tolerance is produced. The immature B cells whose B-cell receptors (BCRs) bind too strongly to self antigens will not be allowed to mature. If B cells are found to be highly reactive to self, three mechanisms can occur.

• Clonal deletion: the removal, usually by apoptosis, of B cells of a particular self antigen specificity.
• Receptor editing: the BCRs of self reactive B cells are given an opportunity to rearrange their conformation. This process occurs via the continued expression of the Recombination activating gene (RAG). Through the help of RAG, receptor editing involves light chain gene rearrangement of the B cell receptor. If receptor editing fails to produce a BCR that is less autoreactive, apoptosis will occur. Note that defects in the RAG-1 and RAG-2 genes are implicated in Severe Combined Immunodeficiency (SCID). The inability to recombine and generate new receptors lead to failure of maturity for both B cells and T cells.

• Anergy: B cells enter a state of permanent unresponsiveness when they bind with weakly cross-linking self antigens that are small and soluble.

Functions[link]

The human body makes millions of different types of B cells each day that circulate in the blood and lymphatic system performing the role of immune surveillance. They do not produce antibodies until they become fully activated. Each B cell has a unique receptor protein (referred to as the B cell receptor (BCR)) on its surface that will bind to one particular antigen. The BCR is a membrane-bound immunoglobulin, and it is this molecule that allows the distinction of B cells from other types of lymphocyte, as well as being the main protein involved in B cell activation. Once a B cell encounters its cognate antigen and receives an additional signal from a T helper cell, it can further differentiate into one of the two types of B cells listed below (plasma B cells and memory B cells). The B cell may either become one of these cell types directly or it may undergo an intermediate differentiation step, the germinal center reaction, where the B cell will hypermutate the variable region of its immunoglobulin gene ("somatic hypermutation") and possibly undergo class switching. Other functions for B cells include antigen presentation, cytokine production and lymphoid tissue organization.

Clonality[link]

B cells exist as clones. All B cells derive from a particular cell, and thus, the antibodies their differentiated progenies (see below) produce can recognize and/or bind the same specific surface components composed of biological macromolecules (epitope) of a given antigen. Such clonality has important consequences, as immunogenic memory relies on it. The great diversity in immune response comes about because there are up to 10⁹ clones with specificities for recognizing different antigens. A single B cell or a clone of cells with shared specificity, upon encountering its specific antigen, divides to produce many B cells. Most of such B cells differentiate into plasma cells that secrete antibodies into blood that bind the same epitope that elicited proliferation in the first place. A small minority survives as memory cells that can recognize only the same epitope. However, with each cycle, the number of surviving memory cells increases. The increase is accompanied by affinity maturation which induces the survival of B cells that bind to the particular antigen with high affinity. This subsequent amplification with improved specificity of immune response is known as secondary immune response. B cells that encounter antigen for the first time are known as naive B cells.

B cell types[link]

A suspected plasma cell. Plasma cells are normally detected in tissue rather than circulation.

• Plasma B cells (also known as plasma cells, plasmocytes, and effector B cells) are large B cells that have been exposed to antigen and produce and secrete large amounts of antibodies, which assist in the destruction of microbes by binding to them and making them easier targets for phagocytes and activation of the complement system. They are sometimes referred to as antibody factories. An electron micrograph of these cells reveals large amounts of rough endoplasmic reticulum, responsible for synthesizing the antibody, in the cell's cytoplasm. These are short lived cells and undergo apoptosis when the inciting agent that induced immune response is eliminated. This occurs because of cessation of continuous exposure to various colony stimulating factors required for survival.

• Memory B cells are formed from activated B cells that are specific to the antigen encountered during the primary immune response. These cells are able to live for a long time, and can respond quickly following a second exposure to the same antigen.

• B-1 cells express IgM in greater quantities than IgG and their receptors show polyspecificity, meaning that they have low affinities for many different antigens. Polyspecific immunoglobulins often have a preference for other immunoglobulins, self antigens and common bacterial polysaccharides. B-1 cells are present in low numbers in the lymph nodes and spleen and are instead found predominantly in the peritoneal and pleural cavities.^[8][9]

• B-2 cells are the conventional B cells most texts refer to.^{[citation needed]}
• Marginal-zone B cells
• Follicular B Cells

Recognition of antigen by B cells[link]

Mechanism of action.

T cell-dependent B cell activation, showing a TH2-cell (left), B cell (right), and several interaction molecules

A critical difference between B cells and T cells is how each lymphocyte recognizes its antigen. B cells recognize their cognate antigen in its native form. They recognize free (soluble) antigen in the blood or lymph using their BCR or membrane bound-immunoglobulin. In contrast, T cells recognize their cognate antigen in a processed form, as a peptide fragment presented by an antigen presenting cell's MHC molecule to the T cell receptor.

Activation of B cells[link]

B cell recognition of antigen is not the only element necessary for B cell activation (a combination of clonal proliferation and terminal differentiation into plasma cells). B cells that have not been exposed to antigen, also known as naïve B cells, can be activated in a T cell-dependent or -independent manner.

T cell-dependent activation[link]

Once a pathogen is ingested by an antigen-presenting cell such as a macrophage or dendritic cell, the pathogen's proteins are then digested to peptides and attached to a class II MHC protein. This complex is then moved to the outside of the cell membrane. The macrophage is now activated to deliver multiple signals to a specific T cell that recognizes the peptide presented. The T cell is then stimulated to produce autocrines (Refer to Autocrine signalling), resulting in the proliferation and differentiation to effector and memory T cells. Helper T cells (i.e. CD4+ T cells) then activate specific B cells through a phenomenon known as an Immunological synapse. Activated B cells subsequently produce antibodies which assist in inhibiting pathogens until phagocytes (i.e. macrophages, neutrophils) or the complement system for example clears the host of the pathogen(s).

Most antigens are T-dependent, meaning T cell help is required for maximal antibody production. With a T-dependent antigen, the first signal comes from antigen cross linking the B cell receptor (BCR) and the second signal comes from co-stimulation provided by a T cell. T dependent antigens contain proteins that are presented on B cell Class II MHC to a special subtype of T cell called a Th2 cell. When a B cell processes and presents the same antigen to the primed T_h cell, the T cell secretes cytokines that activate the B cell. These cytokines trigger B cell proliferation and differentiation into plasma cells. Isotype switching to IgG, IgA, and IgE and memory cell generation occur in response to T-dependent antigens. This isotype switching is known as Class Switch Recombination (CSR). Once this switch has occurred, that particular B cell will usually no longer make the earlier isotypes, IgM or IgD.

T cell-independent activation[link]

Many antigens are T cell-independent in that they can deliver both of the signals to the B cell. Mice without a thymus (nude or athymic mice that do not produce any T cells) can respond to T independent antigens. Many bacteria have repeating carbohydrate epitopes that stimulate B cells, by cross-linking the IgM antigen receptors in the B cell, responding with IgM synthesis in the absence of T cell help. Conjugate vaccines are made to provide a stronger immune response against these foreign molecules. There are two types of T cell independent activation; Type 1 T cell-independent (polyclonal) activation, and type 2 T cell-independent activation (in which macrophages present several of the same antigen in a way that causes cross-linking of antibodies on the surface of B cells).

T cell independent activation type 1 is when a B cell binds to an antigen and receives secondary activation by toll-like receptors; type 2 is when the antigen is a molecule with multiple repeating subunits which can simultaneously cross link enough B cell receptors to fully activate the B cell.

In 2011, it was discovered that immortalized rhesus monkey B cells may be activated by the binding of monoamine ligands to TAAR1, a recently discovered GPCR. They found that methamphetamine, a potent TAAR1 agonist, signals PKA and PKC activation following ligand binding to TAAR1.^[10] Although it is largely recognized as an important regulator of monoaminergic systems, TAAR1 has only recently been characterized as being important for T cell-independent lymphocyte activation.

The ancestral roots of B cells[link]

In an October 2006 issue of Nature Immunology, certain B cells of basal vertebrates (like fish and amphibians) were shown to be capable of phagocytosis, a function usually associated with cells of the innate immune system. The authors postulate that these phagocytic B cells represent the ancestral history shared between macrophages and lymphocytes. B cells may have evolved from macrophage-like cells during the formation of the adaptive immune system.^[11]

B cells in humans (and other vertebrates) are nevertheless able to endocytose antibody-fixed pathogens, and it is through this route that MHC Class II presentation by B cells is possible, allowing Th2 help and stimulation of B cell proliferation. This is purely for the benefit of MHC Class II presentation, not as a significant method of reducing the pathogen load.

Origin of the term[link]

The abbreviation "B" in B cell originally came from Bursa of Fabricius, an organ in birds in which avian B cells mature.^[12] When it was discovered that in most mammals immature B cells are formed in bone marrow, the word B cell continued to be used, although other blood cells also originate from pluripotent stem cells in the bone marrow. The fact that bone and bursa both start with the letter 'B' is a coincidence.

B cell-related pathology[link]

Aberrant antibody production by B cells is implicated in many autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. B cells are also susceptible to malignant transformation.

Additional image[link]

Figure 1: Schematic diagram to explain mechanisms of clonal selection of B cell, and how secondary immune response is stronger, quicker and more specific in comparison with the primary one.^[13]

See also[link]

• Affinity maturation
• Antibody
• Clonal selection
• Original antigenic sin

References[link]

Activation of B Lymphocytes by T-Independent Antigens. Gary Kaiser. American Society for Microbiology. July 2005.

External links[link]

• B-Lymphocytes at the US National Library of Medicine Medical Subject Headings (MeSH)
• B Cells and T Cells
• B Cell Development and Generation of Lymphocyte Diversity
• Interactive Animation of B Cell Maturation (requires Flash video software)
• A Tale of Two SHEPherds (from Beaker Blog)
• Educational Resource on the Biology of Antibody Cells

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (November 2009)

Hong 10 (Real name: Kim Hong-Yeol, Hangul: 김홍열, born on 27 December 1984 in South Korea) is a male South Korean B-boy (also known as Breakdancer).^[1] His accomplishments include both a Red Bull BC One individual title (2006) and a Battle of the Year crew title (2002). He also was a judge at the 2007 Battle of the Year world finals.^[2][3]

Biography[link]

Name[link]

The name Hong 10 comes from using a Korean language homonym and an English language pun. The second syllable of his name, Yeol, has the same pronunciation as the Korean pronunciation for the number ten. Therefore, pronouncing the phrase "Hong 10" in Korean will be the same pronunciation as his real name, Hong-Yeol. However, this nickname is always pronounced in English, so he is referred to as hong-ten regardless of the language context - whether Korean or English or otherwise.

Crew[link]

Hong 10 was in the crew Expression (with which he won the Battle of the Year title in 2002) and is currently in a crew called Drifterz and a project team named Project Soul while he also performs as a solo dancer. Recently he formed a crew called 7 Commandoz with the world renowned bboys Ronnie, Differ, Skim, Wing, Menno, and Dyzee. This crew is known for their special Futuristic style. Recently, he has represented Jinjo Crew with fellow 7 Commandoz members Skim and Wing such as in the UK B-boy Championships 2009, Battle of the Year 2010, and R-16 Korea 2011.

Moves[link]

Some of his signature moves include spinning airchair, spinning reverse airbaby, walking halo freezes, handcuff mills to headspin drills, chair flares, and his signature "Hong 10 Freeze".

History[link]

He first became a well-known bboy during 2002 when he exploded onto the scene being part of the Korean crews that won the then two most prestigious dance competitions in the world - Battle of the Year International and the UK B-Boy Championships. He has also done well in many individual competitions, winning the 2006 Red Bull BC One but more commonly known as the famous 'runner up' having been a finalist at many competitions including three times at the UK B-boy Championships.

List of Notable Achievements[link]

Significant achievements in major events are highlighted in bold text.

2001[link]

• Performance in Dance Dynamite, Japan
• Be.B-Boy, Japan (1st Place)
• Tokyo Dance Delight, Japan (2nd Place, Performance)

2002[link]

• Style War, Korea (1st Place)
• Performance in Big Wax, Japan
• Hip Hop Connection B-boy Master Mixed Battle Vol.1, Korea (1st Place)
• B-Boy Unit Vol.4, Korea (1st Place)
• B-Boy Master Championship, Korea (1st Place)
• Solo battle with Remind in HipHop Connection Vol.3, Korea
• Performance in Dance Dynamite, Japan
• Be.B-Boy, Japan (1st Place)
• Performance in Asian Comment, Denmark
• Guest battle in Jam 2 The Beat, Denmark
• Battle Of The Year 2002 Korea, Korea (1st Place)
• International Battle Of The Year 2002, Germany (1st Place)
• UK B-Boy Championship 2002 Solo Category, UK (2nd Place)
• UK B-Boy Championship 2002 Team Category, UK (1st Place)
• Free Style Session Japan, Japan (2nd Place)
• Take part in Sony Net.MD TV advetisement, New Zealand
• Voted Best B-Boy of the Year

2003[link]

• Distinguished service prize, Honor of Dance 2003, Korea
• Featured on <6'o Clock Focused Issues> MBC TV programme, Korea
• B-Boy Master Mixed Battle Vol.3 Korea (1st Place)
• Performance in <Big Wax>, Fukuoka Japan
• Hiphop Planet, France (1st Place)
• UK B-Boy Championship 2003 Team Category, UK (2nd Place)
• Pro-Am Euro, France (1st Place)
• Judge & Special Guest Battle at the Netherland Tournament

2004[link]

• Performance in <Funky Funky> the musical, Korea
• B-Boy Unit Vol.6, Korea (1st Place)
• B-Boy Challenge Vol.4, Korea (1st Place)
• Guest performance at <Breakin Convention>, UK
• Guest performance at <Fitness Festival>, Italy
• Guest performance <Korea Hip Hop Nite>, Taiwan
• Judge of <B-Boy Battle>, Taiwan
• Guest performance in the launching show of iPod, Korea
• Performed in the opening of <Korean Broadcasting Awards>, Korea
• UK B-Boy Championship 2004 Solo Category (2nd place)
• UK B-Boy Championship 2004 Team Category (1st place)
• Free Style Session, Korea (1st place)
• B-Boy Challenge Grand Championship, Korea (1st place)
• Performance at Nike, Inc. LeBron event, Korea
• Korean representative in <Free Style Session World Final>, Japan

2005[link]

• Participation in <Match One's Skill>, Korea
• Street Dance Summer Jam, Taiwan (1st place)
• Stand-in performance in TV drama <Nonestop>, Korea
• Opening performance for <EBS Robot Battle Korea>, Korea
• Event performance in <Nike 5,6,7,8>, Korea
• Judge of <Yongmasan Battle>, Korea
• Performance in <Breakin' Convension>, UK
• Red Bull BC One 1on1, Germany (2nd place)
• K.O.B.E, Japan (1st place)
• Judge of Battle Of The Year South East Asia 2005, Taiwan
• Participation in International Breakdance Event, The Netherlands
• Hip Hop World Challenge 1on1, Germany (1st place)
• Judge of <Red Bull Street Battle>, Hong Kong
• UK B-Boy Championship Solo Category (2nd place)
• UK B-Boy Championship Team Category (1st place)
• KMTV <Original Move 1on1 vol.7>, Korea (1st place)
• Motion-capture model for PSP game <B-Boy>, UK
• Judge of <MBK 3on3 Battle>, Thailand
• IBE 2005

2006[link]

• One Of The Move vol.2, Korea (1st place)
• Armory Cup Korea 2006, Korea (2nd place)
• Performance in <Breakin Convension>, UK
• SBS <Hope TV> tournament, Korea (1st place)
• Judge of <Top of Top>, Korea
• Took part in KBS TV commercial, Korea
• Red Bull Break in Battle, Ireland (2nd place)
• Took part <Vita 500> commercial, Korea
• UK B-Boy Championship 2006 Korea (1st place)
• Battle Of The Year 2006 Korea, Korea (1st place)
• Performance in <B-Boy Park>, Korea
• Motion-capture model for the game <Groove Party>, Korea
• UK B-Boy Championship 2006 Team Category (2nd place)
• Red Bull BC One 2006, Brazil (1st place)
• Performance Of The Year, Korea (1st place)

2007[link]

• B-Boy Unit Vol.9, Korea (2nd Place)
• Red Bull Beat Battle (1st Place)
• Red Bull BC One 2007 (Semifinalist)

2008[link]

• Red Bull BC One 2008 (Judge)
• IBE 2008

2009[link]

• Jincheon 2009 1st Place (7 Commandos)
• BOTY Taiwan 2009 (judge)
• BOTY Singapore 2009 (judge)
• 2-Oh-Sick Usa 2009 (Steven Chhuon, Jovy Neak, Andy Phriep, j-mart, dino dylan)
• Participation in International Breakdance Event, The Netherlands
• IBE 2009.

2010[link]

• 2010 Vancouver Battle of T.N.G - Just Battle 3 on 3 (judge)
• Be.B-Boy, osaka3on3 (1st Place)
• Be.B-Boy, osaka1on1 (1st Place)
• International Battle of the Year 2010 (1st Place)-With Jinjo Crew

2011[link]

• Temple O'Style, 1st Place (7 Commandoz)
• Break The Floor, 1st Place (7 Commandoz)
• R16 Korea,Champion (Jinjo)
• Red Bull Bc One 2011 (Lost in the first round)

See also[link]

• Bboyworld http://www.bboyworld.com
• Bboytube http://www.bboytube.com
• Red Bull BC One http://www.redbullbcone.com

References[link]