CD23, also known as Fc epsilon RII, or FcεRII, is the low-affinity receptor for IgE, an antibody isotype involved in allergy and resistance to parasites, and is important in regulation of IgE levels.

CD23 is a C-type lectin, and is found on mature B cells, activated macrophages, eosinophils, follicular dendritic cells, and platelets.

CD23 is located on Chromosome 19.

There are two forms of CD23: CD23a and CD23b.

CD23a is present on follicular B cells

CD23b requires IL-4 to be expressed on T-cells, monocytes, Langerhans cells, eosinophils, and macrophages.

CD23 is known to have a role of transportation in antibody feedback regulation.

Antigens which enter the blood stream can be captured by antigen specific IgE antibodies, and the IgE immune complexes that are formed bind to CD23 molecules on B cells, and are transported to the B cell follicles of the spleen.

The antigen is then transf2242ed from CD23+ B cells to CD11c+ antigen presenting cells.

The CD11c+ cells in turn present the antigen to CD4+ T cells, which can lead to an enhanced antibody response.

Increased levels of soluble CD23 cause the recruitment of non-sensitised B-cells in the presentation of antigen peptides to allergen-specific B-cells, therefore increasing the production of allergen specific IgE.

IgE upregulates the cellular expression of CD23 and Fc epsilon RI (high-affinity IgE receptor).

In flow cytometry, CD23 is helpful in the differentiation of chronic lymphocytic leukemia (CD23-positive) from mantle cell lymphoma (CD23-negative).

Lymphomas arising from the mantle zone are generally negative for CD23, but most B-cell chronic lymphomocytic leukaemias and low-grade B-cell lymphomas are positive, allowing immunohistochemistry to distinguish these conditions.

Reed–Sternberg cells are usually positive for CD23.

CD23 expression linked to improved survival in MCL

In a large cohort of patients with mantle cell lymphoma (MCL), CD23 expression was associated with significantly improved survival outcomes.

Mantle cell lymphoma has a distinctive immunophenotype, typically positive for pan B-cell markers, CD5 and cyclin D1, but negative for CD10, CD23, and CD200.

Some MCL cases have atypical immunophenotypic features, such as expression of CD10, CD23, or rarely CD200 or lack of expression of CD5.

Saksena and colleagues found that patients with CD23-positive MCL more frequently had bone marrow involvement 89% vs. 78%, a leukemic nonnodal presentation (42% vs. 11%, an elevated leukocyte count 33% vs. 18%, and stage 4 disease 87% vs. 77%

The researchers reported that CD23 expression was associated with significantly improved PFS and OS.

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