CD23

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. Unlike many of the antibody receptors, CD23 is a C-type lectin. It is found on mature B cells, activated macrophages, eosinophils, follicular dendritic cells and platelets.

There are two forms of CD23: CD23a and CD23b. CD23a is unconditionally present on B cells, while CD23b requires IL-4 to be expressed on T-cells, monocytes, Langerhans cells, eosinophils and macrophages.

The allergen responsible in dust mite allergy, Der-p-1, is known to cleave CD23 from a cells surface. As CD23 is soluble it can move freely and interact with cells in plasma. Recent studies have shown that 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 in turn is known to upregulate the cellular expression of CD23 and Fc epsilon RI (high affinity IgE receptor).