About Cytokines Biology
Cytokines are low molecular weight regulatory proteins or glycoproteins secreted by WBCs and various other cells in the body in response to various stimuli.
Cytokines are a broad category of signaling molecules that are produced by cells of the immune system and other cells throughout the body. They play a critical role in the regulation of immune responses and are involved in a wide range of physiological and pathological processes.
Cytokines are typically small proteins or glycoproteins that are secreted by cells in response to various stimuli, such as infections, injury, or inflammation. They can act locally or travel throughout the body via the bloodstream to affect target cells.
There are many different types of cytokines, including interleukins, interferons, tumor necrosis factors, and chemokines, each with their own specific functions. For example, interleukins are involved in the regulation of immune cell proliferation and differentiation, while interferons are important for antiviral responses.
Cytokines can have both pro-inflammatory effects and anti-inflammatory effects, depending on the context in which they are produced and the specific cytokine involved. Dysregulation of cytokine production and signaling can lead to a variety of immune-mediated diseases, such as autoimmune disorders, allergies, and chronic inflammation.
Historical Background
The activity of cytokines was first discovered in the 1965, when soluble factors found in supernatants extracted from in vitro cultures of lymphocytes, usually proteins or glycoproteins, that could regulate proliferation, differentiation, and maturation of immune system cells.
Production of these factors by cultured lymphocytes was induced by activation with antigens or with nonspecific mitogens (molecules inducing cell division, or mitosis).
However, biochemical isolation and purification of cytokines was initially hampered because of their low concentration in the culture supernatants and the absence of well-defined assay systems for individual cytokines.
The advent of hybridoma technology allowed the production of artificially generated T-cell tumors that constitutively produced IL-2, allowing for its purification and characterization.
Gene cloning techniques developed during the 1980 made it possible to generate pure cytokines by expressing the proteins from cloned genes derived from hybridomas or from normal leukocytes, after transfection into bacterial or yeast cells.
Pure cytokine preparations is used by researchers were able to identify cell lines whose growth depended on the presence of a particular cytokine.
Monoclonal antibodies are specific for many cytokines have made it possible to develop rapid, quantitative, cytokine-specific immunoassays.
ELISA assays measure the concentrations of cytokines in solution, Elispot assays quantitate the cytokines secreted by individual cells, and cytokine-specific antibodies can be used to identify cytokine-secreting cells using intracellular cytokine staining followed by flow cytometry or immuno-fluorescence microscopy.
General Characteristics of Cytokines
- Cytokines are small proteins or glycoproteins with molecular weights ranging from 8 to 80 kDa.
- They are produced by a variety of cells, including immune cells, endothelial cells, and epithelial cells.
- Cytokines act as signaling molecules, transmitting messages between cells.
- They can have autocrine, paracrine, and endocrine effects.
- They have a short half-life, typically ranging from a few minutes to a few hours.
- Cytokines can act alone or in combination with other cytokines to produce specific effects.
- They are involved in a wide range of biological processes, including inflammation, immune responses, haematopoiesis, and cell proliferation and differentiation.
- Cytokines can have both pro-inflammatory effects and anti-inflammatory effects.
- The production and activity of cytokines are tightly regulated by various mechanisms, including feedback loops and signal transduction pathways.
- Dysregulation of cytokine production and signaling can lead to a variety of diseases, including autoimmune disorders, allergies, and chronic inflammation.
Induction Mechanism of cytokines
Cytokines can be induced by 5 types of induction mechanisms of pleiotropy, redundancy, synergism, antagonism, and cascade induction. These induction mechanisms permit them to regulate cellular activity and co-ordination.
Depending on the nature of target cells, cytokines induces different types of biological effects is said to have a pleiotropy induction. If two or more cytokines that mediate similar functions are said to be redundancy induction. Cytokine synergism induction occurs when the combined effect of two cytokines on cellular activity is greater than the additive effects of the individual cytokines. In some cases, the effects of one cytokine inhibit or antagonize the effects of another. Cascade induction occurs when the action of one cytokine on a target cell induces that cell to produce one or more additional cytokines.
Role of Cytokines in immunity
- They are secreted by immune cells and act as signaling molecules that help regulate the immune response.
- When the body encounters a pathogen, such as a virus or bacteria, immune cells are activated and begin to produce cytokines. These cytokines then bind to receptors on other immune cells, triggering a cascade of events that ultimately leads to the elimination of the pathogen.
- Cytokines can also activate other immune cells, such as T cells and B cells, which are essential for the adaptive immune response. For example, interleukin-2 (IL-2) is a cytokine that plays a critical role in the activation and proliferation of T cells.
- In addition to their role in immune activation, cytokines also play a role in regulating the immune response. They can promote inflammation, which is necessary for the elimination of pathogens, but excessive inflammation can lead to tissue damage and disease.
Overall, cytokines are essential for immune activation and regulation, and their dysregulation can lead to a range of immune disorders and diseases.
6 Families and Types of Cytokines
Cytokines are a diverse group of proteins that can be classified into several different categories based on their structure and function. Here are some of the major types of cytokines:
Interleukins
Interleukins (IL) are cytokines that are produced by immune cells and act on other immune cells. They play a crucial role in regulating the immune response by activating immune cells and promoting inflammation. For example, IL-2 promotes the activation and proliferation of T cells, while IL-4 promotes the differentiation of B cells.
Chemokines
Chemokines are cytokines that are involved in the recruitment of immune cells to sites of infection or inflammation. They act by binding to receptors on the surface of immune cells, triggering a signaling cascade that leads to cell migration. Chemokines are also important in the development of the immune system and the regulation of immune cell trafficking.
Interferons
Interferons (IFN) are cytokines that are produced in response to viral infections and other pathogens. They play a key role in the innate immune response by activating antiviral mechanisms and stimulating the production of other cytokines. There are three major types of interferons: IFN-alpha, IFN-beta, and IFN-gamma.
Tumor necrosis factor
Tumor necrosis factor (TNF) is a cytokine that is produced by immune cells and is involved in the regulation of inflammation. It plays a key role in the immune response to pathogens and is also involved in the pathogenesis of many autoimmune and inflammatory diseases.
Growth factors
Growth factors are cytokines that are involved in the development and maintenance of tissues and organs. They stimulate cell proliferation, differentiation, and survival. Examples of growth factors include erythropoietin, which stimulates the production of red blood cells, and granulocyte colony-stimulating factor (G-CSF), which stimulates the production of white blood cells.
Transforming growth factor
Transforming growth factor (TGF) is a cytokine that plays a complex role in the immune system. It can have both pro-inflammatory and anti-inflammatory effects depending on the context. TGF-beta, for example, is a potent immunosuppressive cytokine that can inhibit the activation of T cells and the production of other cytokines.
In summary, cytokines are a diverse group of proteins that play critical roles in the immune system. They are involved in immune activation, regulation, and tissue development and maintenance. The different types of cytokines have unique functions and are essential for a healthy immune response.
FAQs on Cytokines
Answer – There are different types of cytokines, including chemokines, interferons, interleukins, lymphokines and tumor necrosis factor.
