The CC1 monoclonal antibody specifically recognizes carcinoembryonic antigen-related cell adhesion molecule 1a (CEACAM1a or CEACAM1[a]), an allotypic form of CEACAM1 which is also known as CD66a, Murine hepatitis virus receptor (MHV-R), or Biliary glycoprotein 1 (BGP-1). Four known isoforms of mouse CD66a arise from alternative splicing of RNA transcripts encoded by Ceacam1, a member of the carcinoembryonic antigen (CEA) family and Ig gene superfamily. These isoforms are type I transmembrane proteins that include a heavily glycosylated extracellular region with an N-terminal IgV-like domain and up to three IgC2-like domains followed by a transmembrane region and a cytoplasmic tail of relatively short (10 amino acids) or long (73 amino acids) length. The cytoplasmic tails enable interactions with other intracellular molecules to initiate or regulate cellular responses. The two CD66a isoforms with long cytoplasmic tails contain immunoreceptor tyrosine-based inhibitory motifs (ITIMs) that may enable CD66a to function as an immune checkpoint inhibitor. CD66a is expressed on a variety of cell types including certain epithelial cells, endothelial cells, B cells, activated T cells, NK cells, monocytes, dendritic cells (DC), and neutrophils. CD66a (CEACAM1a) is a multifunctional protein. Through their IgV-like domain, CD66a (CEACAM1a) molecules function as homophilic and heterophilic intercellular adhesion molecules. They can also function as MHV-Rs, angiogenic factors, regulators of cellular proliferation and differentiation, and tumor suppressors. Two distinct Ceacam1 alleles, (a and b), exist because of differences in their IgV-like domain gene sequences. Ceacam1a is found in most inbred mouse strains including BALB/c, C57BL/6, and C3H mice whereas Ceacam1b is found in SJL mice. CD66a (CEACAM1a) proteins are specifically bound by the CC1 antibody whereas CEACAM1b proteins are not. The CC1 antibody recognizes an epitope in the N-terminal domain of mouse CD66a (CEACAM1a) proteins.
The antibody was conjugated to BD Horizon™ BUV661 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 661-nm. BD Horizon Brilliant BUV661 can be excited by the ultraviolet laser (355 nm) and detected with a 670/25 filter and a 630 nm LP. Due to cross laser excitation of this dye, there may be significant spillover into channels detecting APC-like emissions (eg, 670/25-nm filter).
Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BUV661 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV661 reagents (eg, CD4 vs. CD45) can have slightly different fluorescence spillover therefore, it may also be necessary to use clone-specific compensation controls when using these reagents.