MW: 11.1kDa (97aa) 18-28kDa (SDS-PAGE under reducing conditions). Purity >90% by SDS-PAGE. MS4A1, also known as B-lymphocyte antigen CD20, is an activated-glycosylated phosphoprotein expressed on the surface of all B-cells beginning at the pro-B phase and progressively increasing in concentration until maturity. It is to enable optimal B-cell immune response, specifically against T-independent antigens. It is suspected that it acts as a calcium channel in the cell membrane. It plays a role in th