Although the cause of multiple sclerosis is still unclear, a variety of genetic risk factors and environmental influences have already been linked to the disease. Studies in recent years have clearly shown that genetic risk variants are a necessary condition for developing MS. A new study shows that these genetic influences, while always present in MS patients, are not on their own sufficient to trigger MS. 

A team of researchers from the Institute of Experimental Immunology at the University of Zürich, Switzerland, and the Institute of Clinical Neuroimmunology at the LMU Klinikum, Germany, examined 61 pairs of monozygotic twins – where one twin is affected by MS whereas the co-twin is healthy. From a genetic point of view, the twins were identical. Using identical twins enabled researchers to rule out the genetic influence and specifically track the immune system changes that were ultimately responsible for triggering MS in one twin.

The researchers found that increased sensitivity to certain cytokines leads to greater activation of T cells in the blood of patients with MS. These T cells are more likely to migrate into the central nervous system of patients and cause damage there. The identified cells were found to have the characteristics of recently activated cells, which were in the process of developing into fully functional T cells.

The findings were published in the journal Nature.