Test Details: Immunohistochemical testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody. CD23, also known as low-affinity IgE receptor, is a type II transmembrane glycoprotein involved in the regulation of IgE response. CD23 is expressed on mature B-lymphocytes, follicular dendritic cells, and activated macrophages. CD23 is an essential marker used to discriminate B-CLL from other lymphoma types with similar morphology. It is also an important marker for follicular dendritic cell tumours.