CD20 is a transmembrane phosphoprotein that is expressed on the surface of B lymphocytes.
The CD20 antigen is present on both resting and activated B lymphocytes but is lost prior to differentiation into plasma cells.
As CD20 expression is restricted to B cells, this antigen is a useful marker or target for B-cell lymphomas.
Studies demonstrate that the expression of CD20 correlates with B-cell lymphoma in dogs.
In human medicine, an anti-human CD20 monoclonal antibody (Rituximab) has been approved by the FDA to treat B-cell non-Hodgkin's lymphoma resistant to other chemotherapy regimens.