Twin study shows genes not solely responsible for multiple sclerosis

Multiple sclerosis (MS) is unlikely to be caused by genetic factors alone, report researchers who studied a 'globally unique' cohort of identical twins.

The team - based at the Institute of Experimental Immunology at the University of Zurich, Switzerland and the Institute of Clinical Neuroimmunology at the Ludwig Maximilian University Klinikum in Munich, Germany – may also have discovered the origins of the T cells that cause MS.

For the study, immunologist Professor Burkhard Becher, from the University of Zurich, and colleagues, examined 61 pairs of identical twins where only one twin was affected by MS. He clarified: 'We are exploring the central question of how the immune system of two genetically identical individuals leads to significant inflammation and massive nerve damage in one case, and no damage at all in the other,'.

Using state-of-the-art single-cell technologies, including mass cytometry and machine learning, to detail the immune profiles of the study participants, the researchers were able to identify characteristic proteins in the immune cells of those with MS. Not only this, but the team could 'decode the totality of all the genes that are switched on in these cells,' explained Florian Ingelfinger, participating PhD candidate at the University of Zurich.

The biggest difference in the immune profiles of the twins with MS compared with their healthy counterparts was a sensitivity to certain cytokine receptors – the network that acts as the 'language' of the immune system, reported the researchers, in the journal Nature.

They found that this led to greater activation of T cells in the blood of the twins with MS, which made the cells more likely to migrate into the central nervous system and cause damage.

These cells also had characteristics of being 'recently activated' rather than fully functional, with Professor Becher stating that: 'we may have discovered the cellular big bang of MS here.'

He continued: 'The findings of this study are particularly valuable in comparison to previous studies of MS which do not control for genetic predisposition. We are thus able to find out which part of the immune dysfunction in MS is influenced by genetic components and which by environmental factors.'

Indeed, a recent study led by Harvard TH Chan School of Public Health researchers and published online in the journal Science found that MS is likely to be caused by infection with the Epstein-Barr virus.