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

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

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.

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.

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