Which statement about plasma cell markers is true?

Which statement about plasma cell markers is true?

• A. Plasma cells commonly express CD20
• B. Plasma cells lack HLA-DR
• C. Plasma cells express CD38 and CD138
• D. Plasma cells express CD3

Answer: (C)

Plasma cell identification hinges on their distinctive surface markers. The most reliable and defining pattern is strong expression of CD38 together with CD138 (syndecan-1) on the cell surface. This combination is routinely used in flow cytometry to recognize plasma cells in normal marrow and in plasma cell disorders. CD3 is a T-cell marker, so plasma cells do not express it. CD20 is a B-cell marker that is typically lost as B cells mature into plasma cells, so plasma cells usually lack CD20. HLA-DR is not a consistent feature of mature plasma cells, and while its absence is common, it is not as definitive as the CD38/CD138 signature. Therefore, the statement that plasma cells express CD38 and CD138 best captures their identifying phenotype.

Plasma cell identification hinges on their distinctive surface markers. The most reliable and defining pattern is strong expression of CD38 together with CD138 (syndecan-1) on the cell surface. This combination is routinely used in flow cytometry to recognize plasma cells in normal marrow and in plasma cell disorders. CD3 is a T-cell marker, so plasma cells do not express it. CD20 is a B-cell marker that is typically lost as B cells mature into plasma cells, so plasma cells usually lack CD20. HLA-DR is not a consistent feature of mature plasma cells, and while its absence is common, it is not as definitive as the CD38/CD138 signature. Therefore, the statement that plasma cells express CD38 and CD138 best captures their identifying phenotype.