CEACAM21 is a member of the family of carcinoembryonic antigen-related cell adhesion molecules (CEACAMs), which are used by several bacterial pathogens to bind and invade host cells. The transmembrane protein directs phagocytosis of several bacterial species that is dependent on the small GTPase Rac. It is thought to serve an important role in controlling human-specific pathogens by the innate immune system. Alternatively spliced transcript variants have been described, but their biological validity has not been determined. Recombinant human CEACAM21 protein, fused to His-tag at N-terminus, was expressed in E.coli.