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Danger Model
The danger model of the immune system proposes that it differentiates between components that are capable of causing damage, rather that distinguishing between self and non-self. History of immunologic models The first major immunologic model was the Self/Non-self Model proposed by Macfarlane Burnet and Frank Fenner in 1949 with later refinement by Burnet. It theorizes that the immune system distinguishes between self, which is tolerated, and non-self, which is attacked and destroyed. According to this theory, the chief cell of the immune system is the B cell, activated by recognizing non-self structures. Later research showed that B cell activation is reliant on CD4+ T helper cells and a co-stimulatory signal from an antigen-presenting cell (APC). Because APCs are not antigen-specific, capable of processing self structures, Charles Janeway proposed the Infectious Non-self Model in 1989. Janeway's theory involved APCs being activated by pattern recognition receptors (PRRs) that r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lymphocyte Activation Simple
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity). They are the main type of cell found in lymph, which prompted the name "lymphocyte". Lymphocytes make up between 18% and 42% of circulating white blood cells. Types The three major types of lymphocyte are T cells, B cells and natural killer (NK) cells. Lymphocytes can be identified by their large nucleus. T cells and B cells T cells (thymus cells) and B cells (bone marrow- or bursa-derived cells) are the major cellular components of the adaptive immune response. T cells are involved in cell-mediated immunity, whereas B cells are primarily responsible for humoral immunity (relating to antibodies). The function of T cells and B cells is to recognize specific "n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated digestion of cell components. In contrast, apoptosis is a naturally occurring programmed and targeted cause of cellular death. While apoptosis often provides beneficial effects to the organism, necrosis is almost always detrimental and can be fatal. Cellular death due to necrosis does not follow the apoptotic signal transduction pathway, but rather various receptors are activated and result in the loss of cell membrane integrity and an uncontrolled release of products of cell death into the extracellular space. This initiates in the surrounding tissue an inflammatory response, which attracts leukocytes and nearby phagocytes which eliminate the dead cells by phagocytosis. However, microbial damaging substances released by leukocytes would crea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adaptive Immune System
The adaptive immune system, also known as the acquired immune system, is a subsystem of the immune system that is composed of specialized, systemic cells and processes that eliminate pathogens or prevent their growth. The acquired immune system is one of the two main immunity strategies found in vertebrates (the other being the innate immune system). Like the innate system, the adaptive immune system includes both humoral immunity components and cell-mediated immunity components and destroys invading pathogens. Unlike the innate immune system, which is pre-programmed to react to common broad categories of pathogen, the adaptive immune system is highly specific to each particular pathogen the body has encountered. Adaptive immunity creates immunological memory after an initial response to a specific pathogen, and leads to an enhanced response to future encounters with that pathogen. Antibodies are a critical part of the adaptive immune system. Adaptive immunity can provide l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apoptosis
Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, DNA fragmentation, and mRNA decay. The average adult human loses between 50 and 70 billion cells each day due to apoptosis. For an average human child between eight and fourteen years old, approximately twenty to thirty billion cells die per day. In contrast to necrosis, which is a form of traumatic cell death that results from acute cellular injury, apoptosis is a highly regulated and controlled process that confers advantages during an organism's life cycle. For example, the separation of fingers and toes in a developing human embryo occurs because cells between the digits undergo apoptosis. Unlike necrosis, apoptosis produces cell fragments called apoptotic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dendritic Cell
Dendritic cells (DCs) are antigen-presenting cells (also known as ''accessory cells'') of the mammalian immune system. Their main function is to process antigen material and present it on the cell surface to the T cells of the immune system. They act as messengers between the innate and the adaptive immune systems. Dendritic cells are present in those tissues that are in contact with the external environment, such as the skin (where there is a specialized dendritic cell type called the Langerhans cell) and the inner lining of the nose, lungs, stomach and intestines. They can also be found in an immature state in the blood. Once activated, they migrate to the lymph nodes where they interact with T cells and B cells to initiate and shape the adaptive immune response. At certain development stages they grow branched projections, the ''dendrites'' that give the cell its name (δένδρον or déndron being Greek for 'tree'). While similar in appearance, these are structures ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CD40L
CD154, also called CD40 ligand or CD40L, is a protein that is primarily expressed on activated T cells and is a member of the TNF superfamily of molecules. It binds to CD40 on antigen-presenting cells (APC), which leads to many effects depending on the target cell type. In total CD40L has three binding partners: CD40, α5β1 integrin and αIIbβ3. CD154 acts as a costimulatory molecule and is particularly important on a subset of T cells called T follicular helper cells (TFH cells). On TFH cells, CD154 promotes B cell maturation and function by engaging CD40 on the B cell surface and therefore facilitating cell-cell communication. A defect in this gene results in an inability to undergo immunoglobulin class switching and is associated with hyper IgM syndrome. Absence of CD154 also stops the formation of germinal centers and therefore prohibiting antibody affinity maturation, an important process in the adaptive immune system. History In 1991, three groups reported discovering ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IL1B
Interleukin-1 beta (IL-1β) also known as leukocytic pyrogen, leukocytic endogenous mediator, mononuclear cell factor, lymphocyte activating factor and other names, is a cytokine protein that in humans is encoded by the ''IL1B'' gene."Catabolin" is the name given by Jeremy Saklatvala for IL-1 alpha. There are two genes for interleukin-1 (IL-1): IL-1 alpha and IL-1 beta (this gene). IL-1β precursor is cleaved by cytosolic caspase 1 (interleukin 1 beta convertase) to form mature IL-1β. Function The fever-producing property of human leukocytic pyrogen (interleukin 1) was purified by Dinarello in 1977 with a specific activity of 10–20 nanograms/kg. In 1979, Dinarello reported that purified human leukocytic pyrogen was the same molecule that was described by Igal Gery in 1972. He named it lymphocyte-activating factor (LAF) because it was a lymphocyte mitogen. It was not until 1984 that interleukin 1 was discovered to consist of two distinct proteins, now called interleukin-1 a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interferon-α
The type-I interferons (IFN) are cytokines which play essential roles in inflammation, immunoregulation, tumor cells recognition, and T-cell responses. In the human genome, a cluster of thirteen functional IFN genes is located at the 9p21.3 cytoband over approximately 400 kb including coding genes for IFNα (''IFNA1, IFNA2, IFNA4, IFNA5, IFNA6, IFNA7, IFNA8, IFNA10, IFNA13, IFNA14, IFNA16, IFNA17'' and ''IFNA21''), IFNω (''IFNW1''), IFNɛ (''IFNE''), IFNк (''IFNK'') and IFNβ (''IFNB1''), plus 11 IFN pseudogenes. Interferons bind to interferon receptors. All type I IFNs bind to a specific cell surface receptor complex known as the IFN-α receptor (IFNAR) that consists of IFNAR1 and IFNAR2 chains. Type I IFNs are found in all mammals, and homologous (similar) molecules have been found in birds, reptiles, amphibians and fish species. Sources and functions IFN-α and IFN-β are secreted by many cell types including lymphocytes (NK cells, B-cells and T-cells), macrophages, fibr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytokine
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrine, paracrine and endocrine signaling as immunomodulating agents. Cytokines include chemokines, interferons, interleukins, lymphokines, and tumour necrosis factors, but generally not hormones or growth factors (despite some overlap in the terminology). Cytokines are produced by a broad range of cells, including immune cells like macrophages, B lymphocytes, T lymphocytes and mast cells, as well as endothelial cells, fibroblasts, and various stromal cells; a given cytokine may be produced by more than one type of cell. They act through cell surface receptors and are especially important in the immune system; cytokines modulate the balance between humoral and cell-based immune responses, and they regulate the maturation, growth, and res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uric Acid
Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates, such as ammonium acid urate. Uric acid is a product of the metabolic breakdown of purine nucleotides, and it is a normal component of urine. High blood concentrations of uric acid can lead to gout and are associated with other medical conditions, including diabetes and the formation of ammonium acid urate kidney stones. Chemistry Uric acid was first isolated from kidney stones in 1776 by Swedish chemist Carl Wilhelm Scheele. In 1882, the Ukrainian chemist Ivan Horbaczewski first synthesized uric acid by melting urea with glycine. Uric acid displays lactam–lactim tautomerism (also often described as keto–enol tautomerism). Although the lactim form is expected to possess some degree of aromaticity, uric acid crystallizes in the lactam form, with computational chemistry also indicating that tautomer to be the most s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenosine Triphosphate
Adenosine triphosphate (ATP) is an organic compound that provides energy to drive many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis. Found in all known forms of life, ATP is often referred to as the "molecular unit of currency" of intracellular energy transfer. When consumed in metabolic processes, it converts either to adenosine diphosphate (ADP) or to adenosine monophosphate (AMP). Other processes regenerate ATP. The human body recycles its own body weight equivalent in ATP each day. It is also a precursor to DNA and RNA, and is used as a coenzyme. From the perspective of biochemistry, ATP is classified as a nucleoside triphosphate, which indicates that it consists of three components: a nitrogenous base (adenine), the sugar ribose, and the Polyphosphate, triphosphate. Structure ATP consists of an adenine attached by the 9-nitrogen atom to the 1′ carbon atom of a sugar (ribose), which i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serum Amyloid A
Serum amyloid A (SAA) proteins are a family of apolipoproteins associated with high-density lipoprotein (HDL) in plasma. Different isoforms of SAA are expressed constitutively (constitutive SAAs) at different levels or in response to inflammatory stimuli (acute phase SAAs). These proteins are produced predominantly by the liver. Acute-phase serum amyloid A proteins Acute-phase serum amyloid A proteins (A-SAAs) are secreted during the acute phase of inflammation. These proteins have several roles, including the transport of cholesterol to the liver for secretion into the bile, the recruitment of immune cells to inflammatory sites, and the induction of enzymes that degrade extracellular matrix. A-SAAs are implicated in several chronic inflammatory diseases, such as amyloidosis, atherosclerosis, and rheumatoid arthritis. Three acute-phase SAA isoforms have been reported in mice, called SAA1, SAA2, and SAA3. During inflammation, SAA1 and SAA2 are expressed and induced principally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
