Researchers on the trail of possible SLE explanation

19 April 2012

In the rheumatic disease SLE, the body is attacked by its own immune system, but until now no-one has been able to explain why. Researchers at Lund University in Sweden could now be on the trail of an explanation.

When the body is affected by serious infections, the immune system is activated. Some of the immune system’s cells throw out a net of DNA and proteins, known as neutrophil extracellular traps (NET), to neutralise foreign bacteria and viruses. In normal cases, the body breaks down the net once it has fulfilled its purpose, but researchers at Lund University have discovered that in some SLE patients, this does not happen. The researchers investigated whether the complement system is in any way involved, explains Jonatan Leffler, a doctoral student at Lund University.

Professor Anna Blom and doctoral student Jonatan Leffler
The complement system is part of the immune system, which can become overactive in some rheumatic diseases. This increases the risk of inflammation, for example in joints and cartilage.

Jonatan Leffler and his colleagues therefore studied one of the most common proteins in the body (C1q), which is part of the complement system, and whether it binds to NET. Their hypothesis proved to be correct.

“Besides the risk of inflammation, the results also suggest that the complement system stimulates the production of antibodies that protect NET and hinder its breakdown. NET can thus remain in the body for longer and can bind more complement proteins, which creates more inflammation and problems for those with SLE. It becomes a vicious circle”, says Jonatan Leffler.

The course of the disease was discovered in the SLE patients with the most severe form of the disease, including kidney problems and inflammation. The research showed that the body’s ability to break down NET varied over time and could be linked to the patients’ relapses.

“The findings make it easier to determine what type of SLE the patient has and could therefore lead to better diagnosis. There is also good reason to continue the research to see if it is possible to develop drugs that can break down NET”, says Jonatan Leffler.

Jonatan Leffler has conducted the study with Anna Blom, Professor of Medical Protein Chemistry, and Anders Bengtsson, a medical doctor and Reader in Rheumatology, both from Lund University. The study was recently published in the Journal of Immunology.

Article: Neutrophil Extracellular Traps that are not Degraded in Systemic Lupus Erythematosus Activate Complement Exacerbating the Disease
Publication: Journal of Immunology

More information
Jonatan Leffler, doctoral student, Lund University, +46 40 337830, Jonatan.Leffler@med.lu.se
Anna Blom, Professor of Medical Protein Chemistry, Lund University, +46 40 338233, +46 704 150682, Anna.Blom@med.lu.se

About SLE (systemic lupus erythematosus)
SLE is a chronic rheumatic disease in which the body’s immune system attacks tissues and organs. Symptoms include redness of the skin, joint pain, kidney problems and organ inflammation. Roughly 90 per cent of those affected are women. In Sweden there are an estimated 6 000 people with SLE.