The purpose of this study is to understand differences in responses to those beginning treatment with ublituximab (Briumvi) as prescribed for Multiple Sclerosis by their treating provider. The study consists of three visits where some questions are asked about experience with Multiple Sclerosis and blood samples are drawn for genetic research and immune cell counts. While taking part in this study, some of the possible risks include those related to having blood drawn, risk of loss of confidentiality and risks related to genetic research.