The Beauchemin laboratory has been characterizing the functions of cell surface receptor proteins named CEACAM1 for carcinoembryonic antigen-cell adhesion molecules. In addition to their role as intercellular adhesion molecules, these proteins also function as negative immune regulators in T and B lymphocytes as well as NK cells, platelets and neutrophils. In addition, these cell surface glycoproteins function as receptors for mouse hepatitis viruses and the human CEACAM1 is the receptor for Neisseria bacteria. Their goal is to understand how CEACAM1 transmits negative regulatory signals to different cell types and the mechanisms by which these proteins perform their function. They are consistently using molecular and cell biology approaches, as well as in vivo genetic manipulation to produce either Ceacam1 gene knockout mice or transgenic mice overexpressing either wild-type or mutant versions of the protein. They are currently involved in the characterization of the associated phenotypes in these animals to understand the functions in an in vivo setting.