Investigating the Effect of Ocrelizumab in African Americans and Caucasians With Relapsing Multiple Sclerosis

Inclusion Criteria: 1. Patients who have chosen to start ocrelizumab and for whom ocrelizumab is determined to be the most appropriate standard-of-care disease modifying therapy (DMT) by the treating neurologist. 2. May be treatment naive, or had suboptimal response to no more than one DMT after an adequate course of treatment (defined as treatment duration of 6+ months). 3. Age 18 to 60 years old. 4. Ethnicity: self-identified as African American or Caucasian. 5. Clinically definite relapsing remitting multiple sclerosis (RRMS) per 2017 revised McDonald criteria. 6. EDSS from 0 to 6 (inclusive) at baseline visit. 7. Able to give informed consent. 8. Able to have MRI scans. Exclusion Criteria: 1. Treatment with another monoclonal antibody, including but not limited to natalizumab, alemtuzumab, daclizumab. 2. Failed 2 or more DMTs. 3. Treatment with immunosuppressant agents, such as chemotherapeutic agents. 4. Claustrophobia. 5. Allergy to contrast. 6. Significant medical problems that the PI determines will interfere with the conduct of the study. 7. Relapse or use of corticosteroids within 30 days prior to baseline visit. 8. Pregnancy. 9. History of kidney or liver insufficiency. 10. History of malignancy.