Which statement describes mature B cell surface markers?

Which statement describes mature B cell surface markers?

• A. IgG and IgD
• B. Alpha and Beta chains
• C. IgM and IgD
• D. CD3

Answer: (C)

Mature B cells present their antigen receptor on the cell surface as membrane-bound immunoglobulins, specifically IgM and IgD. As B cells mature, the same heavy chain gene can be processed to produce both isotypes, so resting B cells coexpress IgM and IgD as their B cell receptors. This combination allows naive B cells to recognize antigen before activation and class switching occurs. IgG and other isotypes arise after activation and switching, so they are not typical surface markers of naive mature B cells. The alpha and beta chains belong to the T cell receptor, and CD3 is a T cell–associated signaling complex, not a B cell marker.

Mature B cells present their antigen receptor on the cell surface as membrane-bound immunoglobulins, specifically IgM and IgD. As B cells mature, the same heavy chain gene can be processed to produce both isotypes, so resting B cells coexpress IgM and IgD as their B cell receptors. This combination allows naive B cells to recognize antigen before activation and class switching occurs. IgG and other isotypes arise after activation and switching, so they are not typical surface markers of naive mature B cells. The alpha and beta chains belong to the T cell receptor, and CD3 is a T cell–associated signaling complex, not a B cell marker.