CD66a, known as CEACAM1a, carcinoembryonic antigen-related cell adhesion molecule 1a, is a glycoprotein of the immunoglobulin superfamily and the carcinoembryonic antigen family. Isoforms expressing either two or four alternatively spliced Ig-like domains in mice have been found in a number of epithelial, endothelial, or hematopoitic tissues. CEACAM1a functions as an intercellular adhesion molecule, an angiogenic factor, and a tumor cell growth inhibitor. It also serves as a signal regulatory protein influencing B cell receptor complex-mediated activation. Moreover, the mouse CEACAM1a protein is targets of viral or bacterial pathogens. It was reported that targeted disruption of the CEACAM1a gene resulting in a partial ablation of the protein in mice led to reduced susceptibility to virus infection. The antibody recognizes the N-terminal domain of murine CEACAM1a, does not recognize murine CEACAM1b, an allele in SJL mice.