CD244 (also known as 2B4 Antigen) is a member of the CD2 subset of the immunoglobulin superfamily (CD2 IgSF). It is expressed on all natural killer (NK) cells, IL-2–activated NK cells (LAK), and a subset of T lymphocytes which mediate non-MHC–restricted cytotoxicity. The C9.1 antibody specifically recognizes CD244.1, the 2B4 alloantigen which is expressed by certain cells in most strains tested (A/J, AKR/N, BALB/c, CBA/N, C3H/He, DBA/1, DBA/2, NZB/N, SJL/J, 129/Svj), but not by cells from C57BL/6 or C58/J mice. The expression of the CD244.1 alloantigen on B lymphocytes that was originally described, has not been confirmed in later studies. The extracellular domain of CD244 is a ligand for another CD2 IgSF member, CD48.
The antibody was conjugated to BD Horizon BUV615 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome with an Ex Max near 350 nm and an Em Max near 615 nm. BD Horizon Brilliant BUV615 can be excited by the ultraviolet laser (355 nm) and detected with a 610/20 filter and a 595 nm LP. Due to the excitation of the acceptor dye by the blue/yellow-green laser line, there may be significant spillover into channels detecting PE-CF594 like emissions (eg, 610/20-nm filter).