CEACAM3 (Carcinoembryonic antigen-related cell adhesion molecule 3) 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. This 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.