Effect of rituximab on the peripheral blood and cerebrospinal fluid B cells in patients with primary progressive multiple sclerosis

Background: Rituximab, an anti-CD20 monoclonal antibody that depletes CD20(+) B cells, has demonstrated efficacy in peripheral neurological diseases. Whether this efficacy can be translated to neurological diseases of the central nervous system with possible autoimmune B-cell involvement remains unknown. Objective: To determine the effect of rituximab on cerebrospinal fluid B cells in patients with multiple sclerosis. Design: Four patients with primary progressive multiple sclerosis were treated with rituximab. Cerebrospinal fluid and peripheral blood B-cell subsets were identified by flow cytometry from each patient before and after rituximab treatment. Results: The B cells in cerebrospinal fluid were not as effectively depleted as their peripheral blood counterparts. Rituximab treatment temporarily suppressed the activation state of B cells in cerebrospinal fluid. The residual B cells underwent expansion after rituximab treatment. Conclusion: The effect(s) of rituximab on the cerebrospinal fluid B-cell compartment is limited in comparison with the effect(s) on the B cells in the periphery, but this finding will need to be confirmed in a larger group of MS patients.