CD19 and myeloid sarcoma: Finally, failed recall response after second exposure was observed for 11 out of 12 aCD20-MS patients receiving continuous treatment with a positive humoral response after first exposure (Figure S4A), and for three out of four participants with their first antigen contact occurring with normal levels of peripheral CD19+ B-cells prior to initiation of anti-CD20 therapy (aCD20-naïve MS) (Figure S4B).