Which surface marker is NOT typically expressed on plasma cells?

Which surface marker is NOT typically expressed on plasma cells?

• A. CD19
• B. CD38
• C. CD138
• D. CD20

Answer: (D)

Plasma cells carry markers that reflect their differentiation from B cells. They reliably express CD38 and CD138, which are classic identifiers of plasma cells. CD19 is typically present on normal plasma cells, reflecting their B-cell origin, so it is commonly expressed. CD20, however, is a B-cell marker that is downregulated as B cells mature into plasma cells and is not expressed on mature plasma cells. Because of this downregulation, CD20 is the marker not typically expressed on plasma cells.

Plasma cells carry markers that reflect their differentiation from B cells. They reliably express CD38 and CD138, which are classic identifiers of plasma cells. CD19 is typically present on normal plasma cells, reflecting their B-cell origin, so it is commonly expressed. CD20, however, is a B-cell marker that is downregulated as B cells mature into plasma cells and is not expressed on mature plasma cells. Because of this downregulation, CD20 is the marker not typically expressed on plasma cells.