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Background
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The human carcinoembryonic antigen (CEA) family is composed of 29 genes tandemly arranged on chromosome 19q13.2 Based on nucleotide homologies, these genes are classified into 2 major subfamilies, the CEACAM and the pregnancy-specific glycoprotein (PSG) subgroups. The CEACAM-encoded proteins include CEA, CEACAM-1, and other CEA gene members. The CEA-related cell adhesion molecule 1, CEACAM-1, is a glycoprotein expressed on the surface of human granulocytes and lymphocytes, endothelia, and many ephitelia, where it has been assigned to the CD66 cluster. CEACAM-1 is involved in the regulation of important biological processes, such as tuomr growth, angiogenesis, and modulation of the immune response. In addition, CEACAM-1 is a receptor of bacteria, such as Neisseria, Haemophilus influenzae, and Moraxella catarrhalis. The binding of Opa (opacity proteins adhesins of N. meninigitidis) occurs at the non-glycosylated face of the N-domain of CEACAM-1, heterophilic adhesion facilitates bacterial colonization of the gut and bacterial phagocytosis by neutrophilis, and is involved in the granulocytes migration during inflammatory responses. The N-terminal domain of CEACAM-1 has been implicated also in mediating homophilic adhesion. This is an important factor for the embryonic organization of the intestinal epithelium and of hepatocytes in the liver, in placental trophoblasts, during muscle and tooth development and vascularization of the central nervous system, in angiogenesis and in the negative regulation of cell proliferation.
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