In addition to immune regulation, Ceacam1 exerts a wide variety of other biological functions. It is a cell-cell adhesion molecule [17, 18] , and a receptor for a variety of commensal and pathogenic microbes in mouse and man [17, 19, 20, 21] . Ceacam1 also regulates angiogenesis [6] , energy homeostasis [22] , and tumor biology [23, 24, 25] . Ceacam1 regulates the tumorigenesis of colon cancers, and is a prognostic factor in lung adenocarcinoma. Tumor expression of Ceacam1 may regulate tumor angiogenesis and invasion, and the expression of both Ceacam1 and CEA by tumors may inhibit the functions of tumor infiltrating lymphocytes.