CD20

Class

Anti-CD20 monoclonal antibody

Pathway

B-cell depletion

CD20 is a cell-surface protein expressed on B lymphocytes, a class of white blood cells responsible for producing antibodies and, in some diseases, for driving damaging immune activity. CD20 appears at a defined stage of B-cell development and is retained on most mature B cells, but it is absent from the earliest precursor cells and from the plasma cells that ultimately secrete antibodies. This expression pattern makes it an attractive target: antibodies directed against CD20 can eliminate the pool of circulating and tissue-resident B cells implicated in disease while sparing the stem-cell compartment needed to regenerate the immune system and largely sparing long-lived plasma cells. Depleting B cells interrupts several disease-relevant processes, including production of harmful autoantibodies, presentation of antigens to other immune cells, and secretion of inflammatory signaling molecules. This rationale underlies the use of anti-CD20 antibodies across B-cell malignancies, where the target cells are themselves the tumor population, and across autoimmune conditions such as those affecting the nervous system or joints, where B cells contribute to disease even though they are not cancerous. Because CD20 does not shed from the cell surface or circulate freely in blood, it remains a stable, accessible target for antibody binding throughout treatment.