Cytokine in the context of Resistin

Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular endothelial cells and a variety of immune cells such as adipose tissue macrophages. Its main role is to store energy in the form of lipids, although it also cushions and insulates the body.

Previously treated as being hormonally inert, in recent years adipose tissue has been recognized as a major endocrine organ, as it produces hormones such as leptin, estrogen, resistin, and cytokines (especially TNFα). In obesity, adipose tissue is implicated in the chronic release of pro-inflammatory markers known as adipokines, which are responsible for the development of metabolic syndrome—a constellation of diseases including type 2 diabetes, cardiovascular disease and atherosclerosis.

Influenza-like illness (ILI), also known as flu-like syndrome or flu-like symptoms, is a medical diagnosis of possible influenza or other illness causing a set of common symptoms. These include fever, shivering, chills, malaise, dry cough, loss of appetite, body aches, nausea, and sneezing typically in connection with a sudden onset of illness. In most cases, the symptoms are caused by cytokines released by immune system activation, and are thus relatively non-specific.

Common causes of ILI include the common cold and influenza, which tends to be less common but more severe than the common cold. Less common causes include side effects of many drugs and manifestations of many other diseases.

The complement system, also known as complement cascade, is a part of the humoral, innate immune system and enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane. Despite being part of the innate immune system, the complement system can be recruited and brought into action by antibodies generated by the adaptive immune system.

The complement system consists of a number of small, inactive, liver synthesized protein precursors circulating in the blood. When stimulated by one of several triggers, proteases in the system cleave specific proteins to release cytokines and initiate an amplifying cascade of further cleavages. The end result of this complement activation or complement fixation cascade is stimulation of phagocytes to clear foreign and damaged material, inflammation to attract additional phagocytes, and activation of the cell-killing membrane attack complex. About 50 proteins and protein fragments make up the complement system, including plasma proteins, and cell membrane receptors. They account for about 10% of the globulin fraction of blood serum.

B cells, also known as B lymphocytes, are a type of lymphocyte. 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 cells, express B cell receptors (BCRs) on their cell membrane. BCRs allow the B cell to bind to a foreign antigen, against which it will initiate an antibody response. B cell receptors are extremely specific, with all BCRs on a B cell recognizing the same epitope.

Chills is a feeling of coldness occurring during a high fever, but sometimes is also a common symptom which occurs alone in specific people. It occurs during fever due to the release of cytokines and prostaglandins as part of the inflammatory response, which increases the set point for body temperature in the hypothalamus. The increased set point causes the body temperature to rise (pyrexia), but also makes the patient feel cold or chills until the new set point is reached. Shivering also occurs along with chills because the patient's body produces heat during muscle contraction in a physiological attempt to increase body temperature to the new set point. When it does not accompany a high fever, it is normally a light chill.

Sometimes a chill of medium power and short duration may occur during a scare, especially in scares of fear, commonly interpreted like or confused by trembling.

The immunoglobulin superfamily (IgSF) is a large protein superfamily of cell surface and soluble proteins that are involved in the recognition, binding, or adhesion processes of cells. Molecules are categorized as members of this superfamily based on shared structural features with immunoglobulins (also known as antibodies); they all possess a domain known as an immunoglobulin domain or fold. Members of the IgSF include cell surface antigen receptors, co-receptors and co-stimulatory molecules of the immune system, molecules involved in antigen presentation to lymphocytes, cell adhesion molecules, certain cytokine receptors and intracellular muscle proteins. They are commonly associated with roles in the immune system. Otherwise, the sperm-specific protein IZUMO1, a member of the immunoglobulin superfamily, has also been identified as the only sperm membrane protein essential for sperm-egg fusion.

A cytokine storm, also called hypercytokinemia, is a pathological reaction in humans and other animals in which the innate immune system causes an uncontrolled and excessive release of pro-inflammatory signaling molecules called cytokines. Cytokines are a normal part of the body's immune response to infection, but their sudden release in large quantities may cause multisystem organ failure and death.

Cytokine storms may be caused by infectious or non-infectious etiologies, especially viral respiratory infections such as H1N1 influenza, H5N1 influenza, SARS-CoV-1, SARS-CoV-2, Influenza B, and parainfluenza virus. Other causative agents include the Epstein-Barr virus, cytomegalovirus, group A streptococcus, and non-infectious conditions such as graft-versus-host disease. The viruses can invade lung epithelial cells and alveolar macrophages to produce viral nucleic acid, which stimulates the infected cells to release cytokines and chemokines, activating macrophages, dendritic cells, and others.

Erythropoietin (/ɪˌrɪθroʊˈpɔɪ.ɪtɪn, -rə-, -pɔɪˈɛtɪn, -ˈiːtɪn/; EPO), also known as erythropoetin, haematopoietin, or haemopoietin, is a glycoprotein cytokine secreted mainly by the kidneys in response to cellular hypoxia; it stimulates red blood cell production (erythropoiesis) in the bone marrow. Low levels of EPO (around 10 mU/mL) are constantly secreted in sufficient quantities to compensate for normal red blood cell turnover. Common causes of cellular hypoxia resulting in elevated levels of EPO (up to 10 000 mU/mL) include any anemia, and hypoxemia due to chronic lung disease.

Erythropoietin is largely synthesized by fibroblast-like type-1 interstitial cells, located primarily in the deep renal cortex in close association with the peritubular capillaries and proximal convoluted tubule; it is also produced in perisinusoidal cells in the liver. Liver production predominates in the fetal and perinatal period; renal production predominates in adulthood. It is homologous with thrombopoietin.

Cell surface receptors (membrane receptors, transmembrane receptors) are receptors that are embedded in the plasma membrane of cells. They act in cell signaling by receiving (binding to) extracellular molecules. They are specialized integral membrane proteins that allow communication between the cell and the extracellular space. The extracellular molecules may be hormones, neurotransmitters, cytokines, growth factors, cell adhesion molecules, or nutrients; they react with the receptor to induce changes in the metabolism and activity of a cell. In the process of signal transduction, ligand binding affects a cascading chemical change through the cell membrane.

Receptor tyrosine kinases (RTKs) are the high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 58 encode receptor tyrosine kinase proteins.Receptor tyrosine kinases have been shown not only to be key regulators of normal cellular processes but also to have a critical role in the development and progression of many types of cancer. Mutations in receptor tyrosine kinases lead to activation of a series of signalling cascades which have numerous effects on protein expression. The receptors are generally activated by dimerization and substrate presentation. Receptor tyrosine kinases are part of the larger family of protein tyrosine kinases, encompassing the receptor tyrosine kinase proteins which contain a transmembrane domain, as well as the non-receptor tyrosine kinases which do not possess transmembrane domains.

Tumor necrosis factor (TNF), formerly known as TNF-α, is a chemical messenger produced by the immune system that induces inflammation. TNF is produced primarily by activated macrophages, and induces inflammation by binding to its receptors on other cells. It is a member of the tumor necrosis factor superfamily, a family of transmembrane proteins that are cytokines, chemical messengers of the immune system. Excessive production of TNF plays a critical role in several inflammatory diseases, and TNF-blocking drugs are often employed to treat these diseases.

TNF is produced primarily by macrophages but is also produced in several other cell types, such as T cells, B cells, dendritic cells, and mast cells. It is produced rapidly in response to pathogens, cytokines, and environmental stressors. TNF is initially produced as a type II transmembrane protein (tmTNF), which is then cleaved by TNF alpha converting enzyme (TACE) into a soluble form (sTNF) and secreted from the cell. Three TNF molecules assemble together to form an active homotrimer, whereas individual TNF molecules are inert.

The adipokines, or adipocytokines (Greek adipo-, fat; cytos-, cell; and -kinos, movement) are cytokines (cell signaling proteins) secreted by adipose tissue. Some contribute to an obesity-related low-grade state of inflammation or to the development of metabolic syndrome, a constellation of diseases including, but not limited to, type 2 diabetes, cardiovascular disease and atherosclerosis. The first adipokine to be discovered was leptin in 1994. Since that time, hundreds of adipokines have been discovered.

Transforming growth factor beta 1 or TGF-β1 is a polypeptide member of the transforming growth factor beta superfamily of cytokines. It is a secreted protein that performs many cellular functions, including the control of cell growth, cell proliferation, cell differentiation, and apoptosis. In humans, TGF-β1 is encoded by the TGFB1 gene.

Sarcopenia (ICD-10-CM code M62.84) is a type of muscle loss that occurs with aging and/or immobility. It is characterized by the degenerative loss of skeletal muscle mass, quality, and strength. The rate of muscle loss is dependent on exercise level, co-morbidities, nutrition and other factors. The muscle loss is related to changes in muscle synthesis signalling pathways. It is distinct from cachexia, in which muscle is degraded through cytokine-mediated degradation, although the two conditions may co-exist. Sarcopenia is considered a component of frailty syndrome. Sarcopenia can lead to reduced quality of life, falls, fracture, and disability.

Sarcopenia is a factor in changing body composition. When associated with aging populations, certain muscle regions are expected to be affected first, specifically the anterior thigh and abdominal muscles. In population studies, body mass index (BMI) is seen to decrease in aging populations while bioelectrical impedance analysis (BIA) shows body fat proportion rising.

B cells, also known as B lymphocytes, are a type of lymphocyte. 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 cells, express B cell receptors (BCRs) on their cell membrane. BCRs allow the B cell to bind to a foreign antigen, against which it will initiate an antibody response. B cell receptors are extremely specific, with all BCRs on a B cell recognizing the same epitope.