CD20 is a protein encoded by the MS4A1 gene which is approximately 33 kDa. CD20 is localised to the cell membrane. It is involved in hematopoietic cell lineage, B-cell development pathways and dendritic cell developmental lineage pathway. This protein falls under the membrane-spanning 4A gene family. It is a B-lymphocyte surface molecule which plays a role in the development and differentiation of B-cells into plasma cells and is specifically expressed in B-cells. Mutations in the MS4A1 gene may be involved in Hodgkin lymphoma. STJ96950 was developed from clone 2F4 and was affinity-purified from mouse ascites by affinity-chromatography using specific immunogen.