A new study suggests certain immune cells play an important role in the early stages of multiple sclerosis. The researchers compared certain T cells in pairs of twins – in which one twin is a person with MS while the other is not – and found specific changes. These findings could open new therapeutic avenues and could be used to develop new diagnostic methods.

MS is a chronic inflammatory disease in which the immune system attacks the central nervous system. This impairs the transmission of signals between the brain and body and can lead to deficits in vision, motor control, sensation, and cognitive impairment. The causes of MS are still not completely understood. A study of identical twins, led by a team of researchers at the Institute of Clinical Neuroimmunology, at LMU University Hospital and Biomedical Center, in Munich, Germany, suggests a type of immune cells, CD8-positive T cells, play a role in the early stages of the disease.

Although it is known that CD8 T cells occur in inflammatory areas in the brains of MS patients, it was unclear what role they play in the disease: Are they a mere by-product or active facilitators of inflammation? And what prompts their entry from the blood into the central nervous system? The LMU team investigated these questions with the help of a unique patient cohort, comparing the CD8 T cells of monozygotic twin pairs, of which one is a person with MS while the other is not.

Genes and the environment partially determine who might get MS. Identical twins offer a unique insight into this, as these factors are largely identical. As the healthy twin has an elevated risk (up to 25 percent) of also developing MS, they allow researchers to probe the early stages of MS.

The researchers analyzed CD8 T cells from blood and cerebrospinal fluid samples taken from the twin pairs. Their results show that CD8 T cells occur with the same specific changes in MS patients and people with early signs of the disease. In addition, they exhibit increased migration ability, promote inflammation, and show activation markers. According to the researchers, these properties show these CD8 T cells are migratory in the blood and are already embarking on their journey to the central nervous system, where we encounter the same cells. The researchers also found this cell type in the brain tissue of MS patients, which indicates lasting changes in the CNS.

Intriguingly, the same CD8 T cells did not only occur in people with MS. They were also present in those who did not yet exhibit any symptoms but in whom there were other signs of inflammation without symptoms being evident. Thus, these cells could be early facilitators of MS before symptoms arise.

According to the authors, these findings could open new therapeutic avenues that involve influencing CD8 T cells to slow or prevent the progress of MS. In addition, CD8 T cells could be used to develop new diagnostic methods that allow MS to be detected early enough to halt irreversible nerve damage.

The findings were published in the journal Science Immunology.