The EBVCS-5 antibody specifically binds to human CD23, the low affinity receptor for human IgE (Fc epsilon RII or FcεRII), which is also known as C-type lectin domain family 4 member J (CLEC4J). CD23 is expressed as a ~45 kDa type II membrane glycoprotein that is present at low density on most normal B lymphocytes and at higher levels on activated B lymphocytes, Epstein-Barr virus (EBV)-transformed lymphoblasts, chronic lymphocytic leukemia (CLL) cells of B-lymphocyte origin, and tonsillar B lymphocytes. CD23 expression is induced on B cells by interleukin-4 (IL-4) and is lost after isotype switching to IgA, IgG, or IgE. The CD23 antigen is not present on immature bone marrow B lymphocytes or on T lymphocytes. CD23 may also be differentially expressed on monocytes, macrophages, eosinophils, platelets, dendritic cells, and Langerhans cells. CD23 can mediate IgE-dependent cytotoxicity and phagocytosis by macrophages and eosinophils. Soluble CD23 (sCD23) can be released by CD23-positive cells as a result of proteolytic cleavage of membrane CD23. Larger fragments of sCD23 (eg, 25-37 kDa) retain their IgE-binding capacity whereas smaller fragments (ie, ≤ 12 kDa) do not. Soluble CD23 may have immunoregulatory effects on the growth and differentiation of B cells and other cell types.
The antibody was conjugated to BD Horizon Red 718, which has been developed exclusively for BD Biosciences as a better alternative to Alexa Fluor® 700. BD Horizon Red 718 can be excited by the red laser (628 – 640 nm) and, with an Em Max around 718 nm, it can be detected using a 730/45 nm filter. Due to similar excitation and emission properties, we do not recommend using R718 in combination with APC-R700 or Alexa Fluor® 700.