Interleukin 6 (IL-6) Protein

April 23, 2020

The interleukin 6 (IL-6) protein is a proinflammatory cytokine and an anti-inflammatory myokine that helps the body regulate immune responses. Interest in testing for IL-6 has grown as providers consider how to treat serious hyperimmune reactions in some patients with COVID-19.

Much of the attention surrounding COVID-19 laboratory testing has focused on two primary areas: viral detection to establish diagnosis and antibody testing to assess previous exposure. As the COVID-19 pandemic continues to evolve, new medical challenges are surfacing, some of which laboratory testing may play a key role in addressing.

One such challenge is addressing a serious hyperimmune reaction in some patients with COVID-19. Providers treating these patients are showing interest in the possible connection between a deadly condition known as a “cytokine storm” and adverse disease outcome.

A cytokine storm is characterized by the profound and uncontrolled release of cytokines, including interleukin 6 (IL-6). In this condition, the immune system is thrown into overdrive, essentially overwhelming the body’s organs. In patients with COVID-19 and other severe respiratory viruses, the resulting pulmonary inflammation makes oxygenation even more difficult and can eventually lead to acute lung injury or acute respiratory distress syndrome (ARDS), among other conditions.

Cytokine testing, though still investigational in nature, may aid in identifying cytokine storm in patients with COVID-19 and guide treatment for the condition before it can become fatal, said Lisa Peterson, PhD, a medical director in ARUP’s Immunology Division. More clinicians are ordering a test for IL-6, a nonspecific marker associated with inflammatory response, to identify patients with suspected cytokine storm.

Traditionally, IL-6 testing has been used primarily for research purposes and to support attempts to understand the pathogenesis of immune, infectious, allergic, or inflammatory disorders, Peterson said. IL-6 is not a diagnostic marker for any specific disease, and researchers are still exploring how to interpret IL-6 testing results in the context of COVID-19.

Some early studies and anecdotal evidence suggest that IL-6 testing results could guide the use of IL-6 inhibitors. These inhibitors could ameliorate the severe lung tissue damage caused by cytokine release without hindering the body’s ability to fight off viral infection.

There are still unknowns surrounding cytokine testing and treatment. IL-6 testing is not yet an established component of COVID-19 care. Nonetheless, a number of academic medical centers are gaining experience with IL-6 testing by ordering the test for critically ill patients with COVID-19 and working toward establishing treatment protocols.

“The connection between COVID-19 and a resulting cytokine storm is an intriguing area of research. Patient care could be positively impacted if a means of identifying and managing cytokine storm is found,” Peterson said. ”Ultimately, however, more studies are needed before it is possible to definitively say what role cytokine testing can play in COVID-19.”

Kelly A. Killian, Sr. Medical Writer and Editor.