Peripheral blood memory B cell frequency predicts conversion from clinically isolated syndrome to multiple sclerosis

Background: Starting from the first attack, activated B cells are found in multiple sclerosis (MS) patients and are associated with disease activity.

Methods: Peripheral blood cells of 17 clinically isolated syndrome (CIS) patients were collected during the first attack. CIS patients were divided as those converting to MS (CIS-MS+, n = 8) and not converting to MS (CIS-MS-, n = 9) in three years. Age-gender matched MS patients (n = 19) and healthy individuals (n = 20) were included as controls. Peripheral blood frequencies of total, immature, naive, unswitched and switched memory B cells, plasmablasts and plasma cells were measured by flow cytometry.

Results: CIS patients showed reduced unswitched memory B cell and plasma cell frequencies. CIS-MS- patients had significantly increased levels of total B cells and suppressed unswitched memory B cell and plasma cell frequencies.

Conclusion: Our results suggest that conversion from CIS to MS occurs due to the inability of the immune system to suppress effector B cell production.