The first patient with relapsing remitting MS had a B-cell count of 1 CD19 B cell/μL at the start of personalized dosing (102 weeks after initiation of ocrelizumab therapy) and 15 cells/μL prior to re-dosing after a dosing interval of 34 weeks (sNfL level was 10.6 pg/mL; previous levels were 18.3 and 12.4 pg/mL; 95% prediction interval in healthy controls of similar age is 4–46 pg/mL). Here, CD19 is linked to relapsing-remitting multiple sclerosis.