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™ BUV805 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 805 nm. BD Horizon Brilliant BUV805 can be excited by the ultraviolet laser (355 nm) and detected with a 820/60 filter and a 770LP.