Human Carcinoembryonic Antigen Related Cell Adhesion Molecule 3 (CEACAM3) Protein

Background

CEACAM3, also known as CD66d, is part of the carcinoembryonic antigen-related cell adhesion molecules (CEACAMs), a subgroup within the immunoglobulin superfamily (IgSF). CEACAM3 is primarily expressed on granulocytes, particularly neutrophils, and plays a crucial role in the innate immune response, specifically in defending against bacterial infections. Unlike other CEACAM family members that are primarily involved in cell-cell adhesion and tumor biology, CEACAM3 is highly specialized for recognizing and mediating the phagocytosis of bacteria, particularly pathogenic Neisseria species, Haemophilus influenzae, and Moraxella catarrhalis. CEACAM3 functions as an opsonin-independent phagocytic receptor, enabling neutrophils to directly recognize and engulf bacteria without the need for antibody or complement opsonization. This receptor is a critical component of the host defense system against specific bacterial pathogens that have evolved to exploit CEACAM family proteins to adhere to host cells.