Interferons |Overview

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Interferons |Overview

  • Interferons are a family of broad-spectrum immunoregulatory and antiviral agents. They were first recognized by the phenomenon of viral interference, where the animals infected with one virus became resistant to the infection by a second unrelated virus.
  • These are signalling proteins.
Interferons |Overview
Interferons

According to their functions, three main types of interferons are determined.

Interferons of I type include the major families of α-interferons (IFN-α) and β-interferons (IFN-β), as well as several minor interferon groups (e.g., omega-interferon).

α-Interferon is produced by leukocytes, while fibroblasts and probably other cell types synthesize β-interferon.

  • Cells start to express alpha- or beta-interferons being infected by a virus. Interferons arise in the extracellular fluid and bind to the specific receptors on the membranes of uninfected neighbouring cells.
  • The bound interferon renders its antiviral effect. Several cellular genes are found to derepress under α- and β-interferon activities allowing the synthesis of novel enzymes. One of them, a protein kinase, catalyzes the phosphorylation of initiation factor and ribosomal proteins necessary for protein synthesis, thereby reducing greatly the viral mRNA translation.
  • Another enzyme, oligoadenylate synthase, accelerates the formation of a short polymer of adenylic acid, which activates a latent endonuclease (RNAse L) that in turn degrades both viral and host mRNA.

Interferon of type II is known as γ-interferon (IFN-γ).

  • It differs strongly from two above-mentioned interferons, exhibiting the traits of typical interleukin. Gamma-interferon is produced by T helper cells of 1 type; it stimulates different cell populations especially macrophages, NK cells, supports conversion of “naive” Th0-cells into Th1 type, thus maintaining cell-mediated inflammation.
  • Also, it enhances the expression of HLA antigens on the cell surface.

Interferons of type III include three lambda interferons (IFN-λ) as well as some other regulatory molecules. They demonstrate evident antiviral activity.

  • The interferons are proven to have a broad scope of actions beyond the control of viral infection.
  • It is clear, for example, those interferon-induced enzymes may inhibit host cell division together with the blockade of viral replication.
  • The interferons may also modulate the activity of other immune cells, e.g. natural killer cells.
Interferons |Overview
Alpha (α)-interferons are produced by cells. infected with viruses which stimulate NK cells. Beta (β)-interferons, secreted by fibroblasts, slow inflammation in a. damaged area. Gamma(γ)-interferons is secreted by T cells and NK cells, stimulate. macrophage activity