SUMMARY, EXPLANATION AND LIMITATIONS:
CD21, also known as CR2, C3d receptor and EBV receptor), is expressed strongly on mature B cells, follicular dendritic cells and weakly on immature thymocytes and T lymphocytes. In B-cell ontogeny, CD21 appears after the pre-B stage, is maintained during peripheral B-cell development and is lost upon terminal differentiation into plasma cells.CD21 expression is also gradually lost after stimulation of B cells in vitro. CD21 functions as receptor for C3d, C3dg and iC3b Complement components, for EBV and for IFNα.CD21 binds to CD23 and associates with CD19, CD81 and Leu13 to form a large signal-transduction complex involved in B cell activation.
Immunogen: Recombinant protein encoding the external domain of human CD21.
Staining pattern: Cell membrane.
Positive control: Tissue sample from tonsil.
This antibody is designed for the specific localization of human CD21 using IHC techniques in formalin-fixed, paraffin-embedded tissue sections.
The CD21 antigen is expressed on mature B cells. The antigen is present with a high density in the follicular dendritic cells (CFD) of B areas of lymphoid tissue. The CD 21 B cells stained moderately and strongly CFD cryostat sections of tissue, while the staining of B cells is reduced or nonexistent in paraffin-embedded sections. Immunostaining of the CFD in FFPE sections is as strong as in cryostat sections of tissue. CD21 immunohistological analysis with the CFD non-Hodgkin’s lymphomas in FFPE sections revealed nodular network usually dense and well defined in the CFD in follicular lymphomas (eg Hodgkin centroblastic / centrocytic) and a diffuse network, weak variable size and some types of lymphoma diffuse (eg centrocytic lymphoma). In non-Hodgkin lymphomas of T origin, the CFD are restricted mainly to the peripheral T cell lymphoma angioimmunoblastic type lymphoma and some cases of pleomorphic.
T lymphoblastic lymphomas, T-CLL and mycosis fungoides are not provided with the network of CFD. Only the nodular lymphocyte-predominant type of Hodgkin’s disease has a characteristic network of CFD.