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Follicular B Cell
Within the immune system, follicular B cells (FO B cells) are a type of B cell that reside in primary and secondary lymphoid follicles (containing germinal centers) of secondary and tertiary lymphoid organs, including spleen and lymph nodes. Antibody responses against proteins are believed to involve follicular B cell pathways in secondary lymphoid organs. Mature B cells from the spleen can be divided into two main populations: FO B cells, which constitute the majority, and marginal zone B-cells, lining outside the marginal sinus and bordering the red pulp. FO B cells express high levels of IgD, and CD23; lower levels of CD21 and IgM; and no CD1 or CD5, readily distinguishing this compartment from B1 B cells and marginal zone B-cells. FO B cells organize into the primary follicles of B cell zones focused around follicular dendritic cells in the white pulp of the spleen and the cortical areas of peripheral lymph nodes A lymph node, or lymph gland, is a kidney-shaped Organ (a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Immune System
The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic worms, and also objects such as wood splinters, distinguishing them from the organism's own healthy biological tissue, tissue. Many species have two major subsystems of the immune system. The innate immune system provides a preconfigured response to broad groups of situations and stimuli. The adaptive immune system provides a tailored response to each stimulus by learning to recognize molecules it has previously encountered. Both use humoral immunity, molecules and cell-mediated immunity, cells to perform their functions. Nearly all organisms have some kind of immune system. Bacteria have a rudimentary immune system in the form of enzymes that protect against bacteriophage, viral infections. Other basic immune mechanisms evolved in ancien ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CD5 (protein)
CD5 is a cluster of differentiation expressed on the surface of T cells (various species) and in a subset of murine B cells known as B-1a. The expression of this receptor in human B cells has been a controversial topic and to date there is no consensus regarding the role of this receptor as a marker of human B cells. B-1 cells have limited diversity of their B-cell receptor due to their lack of the enzyme terminal deoxynucleotidyl transferase (TdT) and are potentially self-reactive. CD5 serves to mitigate activating signals from the BCR so that the B-1 cells can only be activated by very strong stimuli (such as bacterial antigen) and not by normal tissue antigen. CD5 was used as a T-cell marker until monoclonal antibodies against CD3 were developed. In humans, the gene is located on the long arm of chromosome 11. There is no confirmed ligand for CD5 but there is evidence that CD72, a C-type lectin, may be a ligand or that CD5 may be homophilic, binding CD5 on the surface of o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Cells
The list of human cell types provides an enumeration and description of the various specialized cells found within the human body, highlighting their distinct functions, characteristics, and contributions to overall physiological processes. Cells may be classified by their physiological function, histology (microscopic anatomy), lineage, or gene expression. Total number of cells The adult human body is estimated to contain about 30 trillion (3×1013) human cells, with the number varying between 20 and 100 trillion depending on factors such as sex, age, and weight. Additionally, there are approximately an equal number of bacterial cells. The exact count of human cells has not yet been empirically measured in its entirety and is estimated using different approaches based on smaller samples of empirical observation. It is generally assumed that these cells share features with each other and thus may be organized as belonging to a smaller number of types. Classification ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B Cells
B cells, also known as B lymphocytes, are a type of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or inserted into the plasma membrane where they serve as a part of B-cell receptors. When a naïve or memory B cell is activated by an antigen, it proliferates and differentiates into an antibody-secreting effector cell, known as a plasmablast or plasma cell. In addition, B cells present antigens (they are also classified as professional antigen-presenting cells, APCs) and secrete cytokines. In mammals B cells mature in the bone marrow, which is at the core of most bones. In birds, B cells mature in the bursa of Fabricius, a lymphoid organ where they were first discovered by Chang and Glick, which is why the ''B'' stands for ''bursa'' and not ''bone marrow'', as commonly believed. B cells, unlike the other two classes of lymphocytes, T cells and natural killer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Follicular B Helper T Cells
Follicular helper T cells (also known as T follicular helper cells and abbreviated as TFH), are antigen-experienced CD4+ T cells found in the periphery within B cell Lymph_node#Subdivisions, follicles of secondary lymphoid organs such as lymph nodes, spleen and Peyer's patches, and are identified by their constitutive expression of the B cell follicle homing receptor CXCR5. Upon cellular interaction and cross-signaling with their cognate Follicular B cell, follicular (Fo B) B cells, TFH cells trigger the formation and maintenance of germinal centers through the expression of CD40L, CD40 ligand (CD40L) and the secretion of Interleukin 21, IL-21 and Interleukin-4, IL-4. TFH cells also migrate from T cell zones into these seeded germinal centers, predominantly composed of rapidly dividing B cells somatic hypermutation, mutating their Ig genes. Within germinal centers, TFH cells play a critical role in mediating the selection and survival of B cells that go on to differentiate either i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marginal-zone B Cell
Marginal-zone B cells (MZ B cells) are noncirculating mature B cells that in humans segregate anatomically into the marginal zone (MZ) of the spleen and certain other types of lymphoid tissue. The MZ B cells within this region typically express low-affinity polyreactive B-cell receptors (BCR), high levels of IgM, Toll-like receptors (TLRs), CD21, CD1, CD9, CD27 with low to negligible levels of secreted- IgD, CD23, CD5, and CD11b that help to distinguish them phenotypically from follicular (FO) B cells and B1 B cells. MZ B cells are innate-like B cells specialized to mount rapid T-independent, but also T-dependent responses against blood-borne pathogens. They are also known to be the main producers of IgM antibodies in humans. Development and differentiation The spleen's marginal zone contains multiple subtypes of macrophages and dendritic cells interlaced with the MZ B cells; it is not fully formed until 2 to 3 weeks after birth in rodents and 1 to 2 years in humans. In human ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Follicular Dendritic Cell
Follicular dendritic cells (FDC) are cells of the immune system found in primary and secondary lymph follicles (lymph nodes) of the B cell areas of the lymphoid tissue. Unlike dendritic cells (DC), FDCs are not derived from the bone-marrow hematopoietic stem cell, but are of mesenchymal origin. Possible functions of FDC include: organizing lymphoid tissue's cells and microarchitecture, capturing antigen to support B cell, promoting debris removal from germinal centers, and protecting against autoimmunity. Disease processes that FDC may contribute include primary FDC-tumor, chronic inflammatory conditions, HIV-1 infection development, and neuroinvasive scrapie. Location and molecular markers Follicular DCs are a non-migratory population found in primary and secondary follicles of the B cell areas of lymph nodes, spleen, and mucosa-associated lymphoid tissue (MALT). They form a stable network due to intercellular connections between FDCs processes and intimate interaction wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lymph Nodes
A lymph node, or lymph gland, is a kidney-shaped Organ (anatomy), organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that include B cell, B and T cells. Lymph nodes are important for the proper functioning of the immune system, acting as filters for foreign particles including cancer cells, but have no detoxification function. In the lymphatic system, a lymph node is a Lymphatic system#Secondary lymphoid organs, secondary lymphoid organ. A lymph node is enclosed in a fibrous capsule and is made up of an outer cortex and an inner medulla. Lymph nodes become inflamed or enlarged in various diseases, which may range from trivial Pharyngitis, throat infections to life-threatening cancers. The condition of lymph nodes is very important in cancer staging, which decides the treatment to be used and determines the prognosis. Lymphadenopathy refers to gland ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CD21
Complement receptor type 2 (CR2), also known as complement C3d receptor, Epstein–Barr virus receptor, and CD21 (cluster of differentiation 21), is a protein that in humans is encoded by the CR2 gene. CR2 is involved in the complement system. It binds to iC3b (inactive derivative of C3b), C3dg, or C3d.Frank K, Atkinson JP (2001). "Complement system." In Austen KF, Frank K, Atkinson JP, Cantor H. eds. ''Samter's Immunologic Diseases, 6th ed. Vol. 1,'' p. 281–298, Philadelphia: Lippincott Williams & Wilkins, . B cells express CR2 on their surfaces, allowing the complement system to play a role in B-cell activation and maturation. Interactions Complement receptor 2 interacts with CD19, and, on mature B cells, forms a complex with CD81 (TAPA-1). The CR2-CD19-CD81 complex is often called the B cell co-receptor complex,Abbas AK, Lichtman AH (2003). ''Cellular and Molecular Immunology, 5th ed.'' Philadelphia: Saunders, because CR2 binds to opsonized antigens through attached ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B Cell
B cells, also known as B lymphocytes, are a type of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or inserted into the plasma membrane where they serve as a part of B-cell receptors. When a naïve or memory B cell is activated by an antigen, it proliferates and differentiates into an antibody-secreting effector cell, known as a plasmablast or plasma cell. In addition, B cells Antigen presentation, present antigens (they are also classified as professional Antigen-presenting cell, antigen-presenting cells, APCs) and secrete cytokines. In mammals B cells Cellular differentiation, mature in the bone marrow, which is at the core of most bones. In birds, B cells mature in the bursa of Fabricius, a lymphoid organ where they were first discovered by Chang and Glick, which is why the ''B'' stands for ''bursa'' and not ''bone marrow'', as commonly believed. B cells, unl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CD23
CD23, also known as Fc epsilon RII, or FcεRII, is the "low-affinity" biochemistry, receptor for IgE, an antibody isotype involved in allergy and resistance to parasitism, parasites, and is important in regulation of IgE levels. Unlike many of the antibody receptors, CD23 is a C-type lectin. It is found on mature B cells, activated macrophages, eosinophils, follicular dendritic cells, and platelets. There are two forms of CD23: CD23a and CD23b. CD23a is present on follicular B cells, whereas CD23b requires Interleukin-4, IL-4 to be expressed on T-cells, monocytes, Langerhans cells, eosinophils, and macrophages. Function CD23 is known to have a role of transportation in antibody feedback regulation. Antigens which enter the blood stream can be captured by antigen specific IgE antibodies. The IgE immune complexes that are formed bind to CD23 molecules on B cells, and are transported to the B cell follicles of the spleen. The antigen is then transferred from CD23+ B cells to CD11 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Pulp
The red pulp of the spleen is composed of connective tissue known also as the cords of Billroth and many splenic sinusoids that are engorged with blood, giving it a red color. Its primary function is to filter the blood of antigens, microorganisms, and defective or worn-out red blood cells. The spleen is made of red pulp and white pulp, separated by the marginal zone; 76–79% of a normal spleen is red pulp. Unlike white pulp, which mainly contains lymphocytes such as T cells, red pulp is made up of several different types of blood cells, including platelets, granulocytes, red blood cells, and plasma. The red pulp also acts as a large reservoir for monocytes. These monocytes are found in clusters in the Billroth's cords (red pulp cords). The population of monocytes in this reservoir is greater than the total number of monocytes present in circulation. They can be rapidly mobilised to leave the spleen and assist in tackling ongoing infections. Sinusoids The splenic sinusoids, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
