Tetrapass transmembrane phosphoprotein that is fixed in the plasmalemma.

A nonglyosylated member of membrane spanning 4-a family (Ishibashi K).

33-37 kd.

Has both intracellular and extracellular components.

Minimally shed or internalized after being bound by antibody.

Does not circulate in the plasma.

Function remains unknown

Expressed in nearly all B-cell tumors, except B-cell acute lymphoblastic leukemia and multiple myeloma.

Acquired during B cell differentiation.

Expressed on surface of mature B cells and a majority of B cell lymphomas but is not expressed on B-lymphoid stem cells, pro-B-cells and plasma cells.

Over 90% of B cell malignancies express CD20.

Expressed on early pre-B cells, remains through B cell development and is then lost from plasma cells (Tedder TF).

When bound by anti-CD20 antibodY, CD20 does not shed from the cell surface.

When bound to surface antigens they induce apoptosis, complement and antibody dependent cytotoxicity of lymphoma cells.

CD20-its natural ligand not yet identified.

Antigen is not shed into the circulation and sequence mutations are infrequent.

Does not have a critical biologic function.

May regulate the entry of extracellular calcium ions.

Targeting CD20 with monoclonal antibodies does not significantly decrease immunoglobulin production against pathogens and does not harm the development of new B cells.

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