Serum IL-27 and IL-35 levels and disease severity in neuromyelitis optica spectrum disorders

Researchers in 2016 conducted a study to investigate the role that interleukins play in the development of neuromyelitis optica spectrum disorder (NMOSD). Interleukins are a type of protein created by white blood cells that respond when there is a suspected disease in the body. Interleukins have been shown to play an important role in autoimmune diseases. In order to investigate the role of a family of interleukins (IL-12) in the pathology of NMOSD, researchers measured their levels in the blood (serum) and cerebrospinal fluid (CSF) of individuals with NMOSD and assessed their relationship with clinical symptoms presented by these individuals.

In order to complete the study, researchers recruited 45 patients with NMOSD from the Neurology Department of Tianjin Medical University General Hospital from January 2012 to July 2015. These patients had all been diagnosed with NMOSD using identical criteria and had also been receiving similar steroid treatment to manage their diagnosis. Researchers also created a control group of healthy individuals matched for sex and age to compare to the group of patients diagnosed with NMOSD.

The researchers found that serum IL-27 and serum IL-35 levels were lower in individuals with NMOSD than the control group. They also found that serum IL-27 and serum IL-35 levels were similar among individuals who were anti-aquaporin 4 (AQP4) positive and those that were negative. When they separated AQP4 positive people from AQP4 negative people, they found that serum IL-35 levels were significantly lower in AQP4 positive individuals than the control group. While not statistically significant, IL-35 serum levels were lower in AQP4 negative individuals compared to the control group as well. Both IL-27 and IL-35 were below detectable levels in the CSF of people with NMOSD and controls.

After data were collected for serum levels, the researchers performed various statistical analyses in order to know whether the correlation between serum levels of IL-27 and IL-35 and disease severity or corresponding MRI indications were statistically significant.

The study participants showed a negative correlation between levels of IL-27 and disease severity and spinal cord lesion length. This means that as the levels of IL-27 decreased, the disease severity and spinal cord lesion length increased. In addition, researchers saw that levels of IL-35 had a negative correlation between disease severity and annual relapse rate.

The researchers thus concluded that the levels of these two interleukins are decreased in patients with NMOSD, which ultimately means these may be involved in the pathology of NMOSD. The researchers speculate these interleukins may be important in mechanisms that reduce inflammatory responses based on the way they play a role in NMOSD. Dr. Benjamin Greenberg from the University of Texas Medical Center noted that one possible issue with this study is that the individuals in the study were treated with steroids, so it may be possible that the levels of these cytokines may be lower because of the steroids and not because of the NMOSD disease process. Additional studies could control for immunosuppressive treatment.