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™ BB700, which is part of the BD Horizon Brilliant™ Blue family of dyes. It is a polymer-based tandem dye developed exclusively by BD Biosciences. With an excitation max of 485 nm and an emission max of 693 nm, BD Horizon BB700 can be excited by the 488 nm laser and detected in a standard PerCP-Cy™5.5 set (eg, 695/40-nm filter). This dye provides a much brighter alternative to PerCP-Cy5.5 with less cross laser excitation off the 405 nm and 355 nm lasers.