CD20 is a 33-37 kDa non-glycosylated protein present on the surface of normal and malignant B lymphocytes and is a member of the MS4A (membrane-spanning 4-domain family A) protein family. The CD20 protein comprises four hydrophobic transmembrane domains, one intracellular domain, and two extracellular domains (a large loop and a small loop), with both the N- and C-termini located within the cytosol. CD20 is associated with several key molecules, including the major histocompatibility complex class II (MHCII), CD40 molecule, B-cell receptor (BCR), and the C-terminal src kinase-binding protein (CBP). CBP interacts with Src kinases such as LYN, FYN, and LCK.
A deficiency in CD20 has been shown to result in a reduced number of circulating memory B cells, decreased isotype switching of immunoglobulins (Ig), and lower IgG antibody levels. It is also linked to various pathophysiological diseases and disorders.
CD20 plays a crucial role in multiple physiological processes and is thus a promising therapeutic target. The CD20 protein product has the potential to enhance drug discovery efforts in related fields.