CEACAM1 structure and function in immunity and its therapeutic implications

•CEACAM1 is expressed on the surface of a variety of cell types and plays a significant role in mediating cellular adhesion and immune function.•CEACAM1 functions as a molecular rheostat whose net contribution to immune functions is determined by the combination of various CEACAM1 isoforms..•The GFCC’C” surface of the CEACAM1 IgV domain serves as the dominant binding region shared by its homophilic and heterophilic ligands.•Microbes have evolved a diverse array of receptors that target the GFCC’C” surface of the CEACAM1 IgV domain and modulate CEACAM1 function.