CD5-positive B cell subsets in secondary progressive multiple sclerosis

Previous studies have demonstrated that CD5⁺ B cells produce more interleukin (IL)-10 than CD5⁻ B cells and that CD5⁺ B cells confer significant protection against experimental autoimmune encephalomyelitis (EAE). The objective of the present study was to determine whether CD5-positive B cell populations are associated with secondary progressive multiple sclerosis (SPMS) and to explore which subsets on CD5⁺ B cells are associated with SPMS. A total of 26 patients with SPMS, of whom 11 were treated with IFNβ (IFN-SPMS) and 15 were not treated (non-IFN-SPMS), and 19 healthy control (HC) subjects were included in the study. Expression levels of CD11a, CD23, CD25, CD38, CD49d, CD80, CD86, CD138, CCR5, and CXCR5 on CD5⁺ B cells in blood samples were examined by flow cytometry. The percentage of CD5⁺ B cells in the SPMS group was significantly lower than in the HC group. Within the subsets of CD5⁺ B cells, the expression of CD11a in the non-IFN-SPMS group was significantly decreased compared to the HC subjects. Patients with SPMS showed lower CCR5, CD25, and CD138 positivity on CD5⁺ B cells than HC subjects. Our results indicate that CD5⁺ B cell subsets might be associated with pathogenesis of SPMS.