Increased peripheral blood CD5+ B cells predict earlier conversion to MS in high-risk clinically isolated syndromes

Clinically isolated syndrome patients (CIS) with oligoclonal IgG bands (OCGB) are at high risk for clinically definite multiple sclerosis (MS). However, the outcome for individual patients is unpredictable and the search for reliable blood markers predicting early conversion to multiple sclerosis (MS) has clinical relevance. CD5+ B cells (CD5+Bc) are involved in some autoimmune diseases. This study investigated whether high blood CD5+Bc percentage can predict CIS conversion to MS. Fifty-five consecutive CIS showing OCGB were prospectively studied. Every patient underwent a brain MRI study and a flow cytometry analysis of CD5+Bc percentage. Conversion to MS was studied during follow-up. The CD5+Bc percentage was assessed in 40 controls and a cut-off value of 3.5% (mean+2 SD) was calculated. A blood CD5+Bc percentage above this value predicted earlier conversion to MS in the whole group (hazard ratio HR]: 3.40; 95% confidence interval CI]: 1.69-6.68; p=0.0005) and in CIS patients fulfilling three or more Barkhof-Tintoré criteria plus OCGB, who showed higher risk for MS (HR: 3.79; 95% CI: 1.86-15.32; p=0.0018). Multivariate analysis also showed a predictive value for high blood CD5+Bc count (HR: 4.3; 95% CI: 1.9-9.5; p<0.0001). It was concluded that high percentages of CD5+Bc independently associate with increased risk of early conversion to MS in CIS patients with OCGB and Barkhof-Tintoré criteria.