What is Interleukin-6?

Interleukin-6 is a substance produced in response to injury or trauma of tissue by specialized white blood cells called T-cells, as well as macrophages and endothelial cells. As the name implies, this substance is an interleukin. However, it also classified as a cytokine, meaning that it is involved in relaying information between cells as both a signaling molecule and a signaling protein. As such, interleukin-6 may behave as both an anti-inflammatory agent and a pro-inflammatory mediator, depending on certain conditions. While interleukin-6 is manufactured naturally in the body, it can also be synthesized in a laboratory.

Interleukin-6 is known by many other names, including interferon-B2, cytotoxic T-cell differentiation factor, and B-cell stimulatory factor-2, among others. It is also classified as a monomer, meaning that it belongs to a group of organic compounds that can bond with similar molecules to form polymers. Specifically, interleukin-6 is a monomer of 184 amino acids secreted by these specialized cells. This release occurs at a single gene site known as 7p21.

Interleukin-6 plays an important role in regulating cell growth as well as immune functioning. In fact, its release is triggered by tissue damage or infection. Receptor sites are found on the surface of numerous cells throughout the body. From these sites, interleukin-6 transports a variety of proteins through the three major signal transduction pathways: protein kinase C, cAMP/protein kinase A, and calcium release. Each interleukin-6 molecule performs a specific action, depending on the cell that initiated its release.

The circulation of interleukin-6 stimulates the immune system by promoting what is known as the acute-phase reaction. This process encourages the production and release of acute-phase proteins, which behave as generic antibodies. In particular, the release of c-reactive protein increases phagocytosis, the process by which certain cells surround and neutralize invading bacteria and other pathogens. This results in an acute-phase response, such as fever. This is due to increased energy distribution in muscle and fatty tissue, which causes body temperature to rise.

Interleukin-6 is also known as a myokine, a type of cytokine triggered by muscle contraction and then discharged into the bloodstream. This exchange promotes a variety of biologic actions. For one thing, it increases the breakdown of fats. It also improves insulin resistance, resulting in better uptake and utilization of glucose. Therefore, interleukin-6 therapy may have an application in treating certain conditions, such as obesity and diabetes type II.

While interleukin-6 is vital for optimum immune functioning, the downside is having too much of a good thing. Impaired or uncontrolled interleukin-6 gene expression can produce unwanted immune responses and lead to a variety of diseases, including autoimmune disorders. Patients with rheumatoid arthritis, for example, typically have elevated levels of interleukin-6 in their synovial tissue. To combat this dysfunction, researchers continue to investigate different ways to inhibit binding of interleukin-6. This includes development of an anti-interleukin-6 receptor antibody.