The 5D3/CD338 monoclonal antibody specifically binds to an epitope of ABCG2 (BCRP1), a multi-drug resistance protein that is a member of ATP binding cassette (ABC) transporters. It is highly expressed on primitive stem cells as identified by the "side-population" (SP) phenotype. This SP phenotype is based on the efflux of fluorescent dyes such as Rhodamine 123 and Hoechst 33342. The expression of ABCG2 appears to be highly conserved as it has been identified in various species. Studies show that highly purified murine stem cells express BCRP1 mRNA and this expression declines sharply as the stem cells express CD34. The highest levels of BCRP1 mRNA expression have been seen in KDR+ human stem cells. ABCG2/BCRP1 was clustered as CD338 in the HLDA8 workshop.
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.