B-lymphocyte antigen CD20 encoded by the MS4A1 gene is an activated-glycosylated phosphoprotein on the surface of all B-cells. The function of the membrane protein is to stimulate B-cell immune response, specifically against T-independent antigens though its natural ligand remains unknown. CD20 is important for the development and differentiation of B-cells into plasma cells. CD20 belongs to the membrane-spanning 4A family with common structural features, similar intron/exon splice boundaries, and unique expression patterns among hematopoietic cells and nonlymphoid tissues.Rituximab, a chimeric anti-CD20 monoclonal antibody, destroys B cells and is used to treat diseases with excessive numbers of B cells, overactive B cells, or dysfunctional B cells, such as many lymphomas, leukemias, transplant rejection, and autoimmune disorders.
