Interferons (IFN) are endogenous tissue hormones composed of short-chain polypeptides, proteins and glycoproteins of up to 166 amino acids. Because of their properties and effects in human metabolism, they are considered to be cytokines along with interleukins that have comparable properties and effects and with other groups of substances.
Cytokines initiate and control immune responses of the immune system and thus perform vital tasks. Interferons can be divided into the three classes IFN-alpha, also called leukocyte IFN, IFN-beta and IFN-gamma. While most of the 23 known IFN-alpha variants are proteins with 166 amino acids each, the beta and gamma IFN consist predominantly of glycoproteins with likewise 166 amino acids, or 144 amino acids in the case of gamma IFN. Interferons are important for the detection and control of viruses and cancerous tumors.
Interferons stimulate and direct complex immune responses in specialized cells of the immune system or directly in the tissue cells affected by viruses or other pathogens or in degenerated tumor cells. The interferons do not have to penetrate into the target cells to stimulate and "distribute their messages", but only dock at specific receptors.
In combination with interleukins, colony-stimulating factors, tumor necrosis factors and chemokines, which together form the class of cytokines, interferons very significantly initiate and control the immune responses to cells affected by viruses or other pathogens. The same applies to cells that have been identified as tumoral.
Interferons are comparable to interleukins in their mode of action, but interferons show a certain specialization in virus infestation and tumor tissue. For humans, the body's own virus and cancer control has a high - and sometimes vital - importance. The immune response that interferons provide is very complex. Interestingly, interferons usually do not fight invading viruses directly, but attach to specific receptors on the cells, causing them to produce certain, antivirally-effective, proteins (enzymes) that help affected cells disrupt the virus through certain metabolic processes or even render them harmless,
This process can also take place in adjacent, non-infected, cells, so that they can thus protect against infestation. Alf- and beta-IFN provides the cells with their activities a guided help for self-help. Gamma interferons are a tissue hormone specializing in the activation and support of macrophages.
Alpha interferons are secreted not only by immune cells but also by many other tissue cells, especially cells infected with viruses or bacteria. IFN-alpha stimulates infested and adjacent cells to produce certain protein-degrading enzymes to break down viral RNA and prevent viruses from replicating their RNA. Even bacterial membranes can be partially dissolved or whole bacteria can be rendered harmless by phagocytes and transported away.
Beta-interferons, also referred to as fibroblast interferons, are predominantly secreted by the extracellular space and virus-infected fibroblasts. The properties and effects of IFN-beta are very similar to those of IFN-alpha. You can even dock on some of the IFN-alpha receptors. The properties of gamma interferons differ from those of IFN-alpha and IFN-beta. IFN-gamma is predominantly secreted by TH1 cells, which are part of the adaptive immune system. The gamma-interferon is always formed when in contact with antigen-presenting macrophages.
This is always the case, for example, with bacteria phagocytating macrophages. In addition to antiviral and antitumoral properties, IFN-gamma also has immunomodulatory effects because it supports the adaptive cells of the immune system, which have adapted and adapted to the fight against current pathogens.
In combination with interleukins and other cytokines, interferons initiate and control reactions of the immune system, the so-called immune response. These are in part extremely complex processes involving many actors involved. It is therefore likely that individual steps of the immune response may be disturbed, or that the immune system as a whole may be under-reacting or over-reacting.
Disturbances in both directions can lead to mild to severe symptoms and illnesses. Since most interferons also cross the blood-brain barrier, disturbances in the release of interferons can also have considerable psychological effects and - in case of weakening - their protective function in the CNS no longer or only to a limited extent. On the other hand, artificially supplied interferons are also used for therapeutic purposes such as in multiple sclerosis (MS) and hepatitis C and B. Symptoms that are similar to interferon production may be similar if only the functionality of the receptors on the cell membranes is disturbed. There are several genetic defects known that lead to dysfunction of certain receptors and cause corresponding deficiency symptoms.
Interferons then can not dock or "find no cells" to which they have to attach themselves in order to perform their tasks. In certain chronified viral diseases (Epstein Barr virus, zoster, herpes, Borrelia and others) already has a disturbed balance between interferon and interleukin-secreting Th1 and Th2 cells. Similar observations have also been made in HIV infections. The homeostasis between the different cytokines is thus of great importance.
With regard to possible systemic overproduction of interferons, which are not caused by local inflammation, so-called "gain mutations" have become known. The mutations lead to an altered - usually massively expanded - secretion of certain interferons, which can be life-threatening.