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™ BUV496 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 with an Ex Max of 348-nm and an acceptor dye with an Em Max at 496-nm. BD Horizon BUV496 can be excited by the ultraviolet laser (355 nm) and detected with a 515/30 nm filter with a 450LP. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into the channel detecting BD Horizon V500 or BV510 (eg, 525/40-nm filter). However, the spillover can be corrected through compensation as with any other dye combination.