Cytokines are a group of soluble polypeptides that are produced by different types of cells (e.g., lymphocytes, macrophages, mast cells, epithelial cells). Cytokines play a regulatory role in the immune system - they control the lymphocyte response to the antigen, are cytotoxic, pro-inflammatory or anti-inflammatory, and supervise intercellular communication.
Cytokinesfunction as mediators of the inflammatory process and the immune response, and influence the growth, proliferation and differentiation of other cells in our body. They can be divided into interleukins, growth factors, interferons, chemokines and the so-called TNF (Tumor Necrosis Factor) superfamily.
Cytokines: split
- Interleukins
Interleukins are cytokines that are produced and released by leukocytes. They are involved in the transmission of information between leukocytes. What's more, their concentration in the blood increases significantly during an infection or injury. Due to the short half-life, they are difficult to determine in blood.
- Growth factors
Growth factors (GM-CSF, G-CSF, M-CSF, SCF) are produced by lymphocytes and macrophages. They show an effect on the proliferation and differentiation of leukocytes in the bone marrow and the functions of mature cells of the immune system.
- Interferons
Interferons are proteins that are usually released in the course of a viral infection. They have antiviral, anti-cancer and anti-proliferative properties. There are two types of interferons.
Type I includes interferon α, β, ε, ω, κ - they are produced by fibroblasts, keratinocytes and dendritic cells. In contrast, type II includes interferon γ, which is produced by NK cells, T cells and antigen-stimulated macrophages.
Interferons intensify the processes of cytotoxicity, phagocytosis and increase the expression of MHC antigens. Moreover, they influence the secretion of other cytokines important in the induction and inhibition of the inflammatory process.
- Superfamily of TNF particles
The superfamily of TNF (tumor necrosis factor) molecules are a large group of cytokines that are produced by T lymphocytes, NK cells, macrophages and monocytes. It has a complex influence on a number of elements of the answerimmunological. For example, TNFα, in addition to its anti-tumor activity, is one of the major cytokines of the inflammatory response. In addition, it plays a role in the pathogenesis of many immunological diseases, such as, for example, transplant rejection, autoimmune diseases, septic shock.
- Transforming Growth Factor TGFβ
An important cytokine that does not belong to the above division is the Transforming Growth Factor (TGFβ). It is produced by B and T lymphocytes, macrophages, neutrophils and platelets. Its main function is to inhibit the production of other cytokines, inhibit the proliferation of B, T and NK cells, and inhibit the expression of MHC class II antigens. , IL-1, IL-6) or anti-inflammatory - inhibiting the development of inflammation (TGFβ, IL-1ra, IL-10, IL-19, IL-20, IL-22, IL-24, IL-26, IL-28, IL-29).
Cytokines can also be divided into those involved in the cytotoxic response (IL-11, IFNα, IFNβ, IFNω, IFNγ, IL-28A, IL-28B, IL-29), involved in the humoral response (e.g. -7, IL-11, IL-21) and cellular (IL-2, IL-16, IL-17 and IFNγ).
Cytokines: action
Cytokines affect cells thanks to the presence of special receptors on their surface. These receptors are made up of two domains - the extracellular domain, which is responsible for binding specificity, and the intracellular domain, which regulates signal transduction to the cell.
Additionally, the so-called pathways of GTPases and mitogen-activated protein kinases (MAPK), tyrosine kinases, phosphatidylinositol-3-kinases and STAT proteins.
After the cytokine binds to the appropriate receptor, a signal is transmitted that stimulates or inhibits cell functions.
Each cytokine, depending on what receptor it binds to, can fulfill different functions. Most of them show the so-called pleiotropic action.
This means that they affect different cells differently, one cytokine can have different activities and affect many types of cells.
In addition, cytokines can act autocrine - that is, affect the cells that secrete them, paracrine - on neighboring cells, and endocrine - in places distant from the source of production.
Many of them are interdependent and form a cytokine network that is important for both the immune response and inflammation.