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 Red 718, which has been developed exclusively for BD Biosciences as a better alternative to Alexa Fluor® 700. BD Horizon Red 718 can be excited by the red laser (628 – 640 nm) and, with an Em Max around 718 nm, it can be detected using a 730/45 nm filter. Due to similar excitation and emission properties, we do not recommend using R718 in combination with APC-R700 or Alexa Fluor® 700.