CD23 – Antibody Lexicon

Synonyms: low affinity IgE receptor, Leu-20, FcεRII

by Assia Bassarova

Background

CD23 is a type II integral membrane single chain glycoprotein with molecular weight of 45 kDa. Two subtypes, FcεRIIa/CD23a and FcεRIIb/CD23b, have been identified. They differ in tissue-specific gene expression and regulation. FcεRIIa is believed to be constitutively expressed only in normal B-cells, B-cell lines (perhaps follicular dendritic cells), and eosinophils, whereas FcεRII b is induced in various cell types. The human FcεRII/CD23 gene has been mapped to chromosome 19p13.3. CD23 is the only FcR which does not belong to the immunoglobulin gene superfamily. CD23 may exist on cell membranes as a dimer or trimer. It also exists as a soluble excreted form that display autocrine promoting activity. CD23 appears to mediate various forms of IgE-mediated immunity. Expression of CD23 on blood lymphocytes, alveolar macrophages, airway smooth muscle cells, and even serum soluble CD23 have been linked to allergic diseases. CD23 is a B-cell-specific antigen and it has essential roles in the regulation of IgE production and in the differentiation of B-cells. In the B cell compartment, sCD23 sustains the growth of activated mature B lymphocytes, possibly via an autocrine mechanism, promotes differentiation of germinal center centroblasts towards the plasma cell pool [in association with interleukin (IL)-1α, and allows B cell precursors to evade apoptosis. In other lineages, sCD23 promotes differentiation of myeloid precursors, thymocytes and bone marrow CD4⁺ T cells, again in association with IL-1α, and also drives cytokine release by monocytic cells. CD23 is upregulated in Eppstein-Barr infection. CD23 is constitutively expressed by intestinal epithelial cells and its expression is enhanced in enteropathies.

Staining in normal cells/tissues

It is widely distributed in various human cells, including B-cells, monocytes and macrophages, eosinophils, platelets, epidermal Langerhans’ cells, follicular dendritic cells, keratocytes, and even airway smooth muscle cells.

Staining in tumors

Many reports suggest that elevated CD23, either on neoplastic cell surfaces or as a soluble form, is a useful marker in either diagnosis or prognosis of disease. CD23 is typically expressed in chronic lymphocytic leukemia (CLL), sometimes in follicular lymphoma, rarely in marginal zone and lymphoplasmacytic lymphoma. Some recent reports have shown low CD23 expression even in mantle cell lymphoma. In CLL, the strongest expression is characteristically present in proliferation centers. It was recently demonstrated that patients with CD23-positive diffuse large B-cell lymphoma have good prognosis. CD23 is also frequently used to demonstrate benign follicular dendritic cells in the background of follicular lymphoma, marginal zone lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, follicular T-cell lymphoma. Together with CD21, CD23 is a marker of rare follicular dendritic cell tumors.

Staining pattern

Strong membranous staining in the follicular dendritic cells and at least weak to moderate staining in the activated B-cells of the mantle zones.

Control tissue

Appendix / tonsil is recommended tissue control for CD23. The follicular dendritic cells of the germinal centers must be stained as strongly as possible. In the mantle zone, the activated B-cells must show an at least weak to moderate and distinct continuous membranous staining reaction. The T-cell areas and squamous / glandular epithelial cells must be completely negative.

Application

In diagnostic pathology CD23 is primarily used in the panel for small B-cell lymphoproliferative disorders.

by Assia Bassarova

Background

Staining in normal cells/tissues

Staining in tumors

Staining pattern

Control tissue

Application

Selected references