The purpose of this study is to assess effects of B cell depletion on the immune system in patients with relapsing forms of multiple sclerosis (MS) treated with ocrelizumab. This will be done by collecting blood from patients starting treatment with ocrelizumab before the first infusion and before the infusions at 6 and 12 months. The effects on the immune system will be assessed by performing transcriptome profiling of immune cells, measuring serum levels of microRNAs, and analyzing serum autoantibody immune signatures using antigen arrays. In addition, blood will be collected once from a group of healthy individuals to serve as controls.

Inclusion Criteria:

• Patients with relapsing form of MS starting treatment with ocrelizumab at Partners MS Center
• Healthy controls
• Ability to understand and sign informed consent

Exclusion Criteria - All subjects:

• Other concomitant autoimmune or inflammatory diseases
• Ongoing treatment with other immunomodulatory medications
• Previous treatment with rituximab, methotrexate, cyclophosphamide, mitoxantrone, mycophenolate mofetil, or alemtuzumab
• Pregnancy or lactation
• Hypersensitivity to ocrelizumab

Exclusion Criteria - Healthy Controls:

• MS
• First-degree relatives with MS

Patients with relapsing form of MS starting treatment with ocrelizumab at Partners MS Center